In case there is any confusion, this is what the Catechism says. This is what the Church teaches. If the Catechism is wrong, then I can do no better and I will just go down with the ship.
2362 "The acts in marriage by which the intimate and chaste union of the spouses takes place are noble and honorable; the truly human performance of these acts fosters the self-giving they signify and enriches the spouses in joy and gratitude."144 Sexuality is a source of joy and pleasure:
The Creator himself . . . established that in the [generative] function, spouses should experience pleasure and enjoyment of body and spirit. Therefore, the spouses do nothing evil in seeking this pleasure and enjoyment. They accept what the Creator has intended for them. At the same time, spouses should know how to keep themselves within the limits of just moderation.145
God created sex to be pleasurable, therefore, God intended for married couples to enjoy sex and seeking sexual pleasure in marriage is a good thing, provided that spouses do not pursue their own pleasure to the point where their mutual love and unity is forgotten (i.e. the limits of just moderation).
2363 The spouses’ union achieves the twofold end of marriage: the good of the spouses themselves and the transmission of life. These two meanings or values of marriage cannot be separated without altering the couple’s spiritual life and compromising the goods of marriage and the future of the family.
The conjugal love of man and woman thus stands under the twofold obligation of fidelity and fecundity.
2366 Fecundity is a gift, an end of marriage, for conjugal love naturally tends to be fruitful. A child does not come from outside as something added on to the mutual love of the spouses, but springs from the very heart of that mutual giving, as its fruit and fulfillment. So the Church, which "is on the side of life"150 teaches that "each and every marriage act must remain open ‘per se’ to the transmission of life."151 “This particular doctrine, expounded on numerous occasions by the Magisterium, is based on the inseparable connection, established by God, which man on his own initiative may not break, between the unitive significance and the procreative significance which are both inherent to the marriage act.”
All sexual activity in a marriage must be BOTH for the good of the spouses and open to life. Separating the procreative from the act is sinful,
but so is having procreative sex when it is not for the good of the spouses. EVERY act must be “open” to the transmission of life and man
on his own initiative may not break it.
2367 Called to give life, spouses share in the creative power and fatherhood of God.153 "Married couples should regard it as their proper mission to transmit human life and to educate their children; they should realize that they are thereby cooperating with the love of God the Creator and are, in a certain sense, its interpreters. They will fulfill this duty with a sense of human and Christian responsibility."154
Couples are called to both generously create new life and to responsible parenthood.
2368 A particular aspect of this responsibility concerns the regulation of procreation. For just reasons, spouses may wish to space the births of their children. It is their duty to make certain that their desire is not motivated by selfishness but is in conformity with the generosity appropriate to responsible parenthood. Moreover, they should conform their behavior to the objective criteria of morality.
As part of the Church’s their duty responsible parenthood, couples may plan their families and avoid pregnancy. However, they must carefully discern whether they are avoiding pregnancy for good, responsible, “just” reasons or out of selfishness. Furthermore, they must use moral means to avoid pregnancy.
2370 Periodic continence, that is, the methods of birth regulation based on self-observation and the use of infertile periods, is in conformity with the objective criteria of morality.157 These methods respect the bodies of the spouses, encourage tenderness between them, and favor the education of an authentic freedom. In contrast, “every action which, whether in anticipation of the conjugal act, or in its accomplishment, or in the development of its natural consequences, proposes, whether as an end or as a means, to render procreation impossible” is intrinsically evil.
Natural Family Planning is moral and encouraged. Contraception, which interferes with the conjugal act to make conception impossible is intrinsically evil. But this does not necessarily include ALL sexual activities that are not open to life. Some are not contraception, but forms of masturbation, which is a different sin.
2351 Lust is disordered desire for or inordinate enjoyment of sexual pleasure. Sexual pleasure is morally disordered when sought for itself, isolated from its procreative and unitive purposes.
2352 By masturbation is to be understood the deliberate stimulation of the genital organs in order to derive sexual pleasure. "Both the Magisterium of the Church, in the course of a constant tradition, and the moral sense of the faithful have been in no doubt and have firmly maintained that masturbation is an intrinsically and gravely disordered action."137 “The deliberate use of the sexual faculty, for whatever reason, outside of marriage is essentially contrary to its purpose.” For here sexual pleasure is sought outside of "the sexual relationship which is demanded by the moral order and in which the total meaning of mutual self-giving and human procreation in the context of true love is achieved."138
To form an equitable judgment about the subjects’ moral responsibility and to guide pastoral action, one must take into account the affective immaturity, force of acquired habit, conditions of anxiety, or other psychological or social factors that lessen or even extenuate moral culpability.
Masturbation (including mutual masturbation) is sexual stimulation outside of the context of the marriage relationship (i.e. the context of married intercourse). It is based in lust and is a sin. But it is NOT contraception. While contraception is “intrinsically evil”, masturbation is merely “intrinsically gravely disordered”. The catechism goes on further to mention mitigating factors, such as immaturity, habit, anxiety, and other psychological or social factors. If such factors apply to an individual, they certainly apply to married couples together.
IMHO, the difference between the two is whether the act itself carries a risk of pregnancy or whether it is interference with an act that can lead to pregnancy. If either is the case, it is contraception, if not, it is masturbation. For example, withdrawal is a form of contraception, even though climax is brought outside of intercourse. It is interference with the natural procreative act. Oral sex (to completion, outside the context of intercourse), on the other hand, is a form of masturbation. The act is inherently non-procreative stimulation of the genitals and there is no interference with anything.
So, from the Catechism, we can draw the following conclusions:
Intercourse = Objectively licit act at all times. Designed to be mutually loving and pleasurable. May or may not be
subjectively sinful based on external conditions and if the intent of the spouses is incompatible with the unitive aspect of marital relations. As for procreation, a procreative action shows procreative intent, no matter what is on the spouse’s mind.
NFP = Always objectively licit and encouraged, but may be subjectively sinful if done out of selfishness. This is a sin of selfishness, not contraception. However, because according to the Catechism, practicing the periodic continence of NFP is completely contrary to an attitude of selfishness, I believe it is unlikely that many couples could use it for selfish reasons.
Contraception = Always intrinsically
evil. Period.
Masturbation = Always intrinsically
gravely disordered and sinful, but there may be mitigating factors that reduce culpability.
