The Church teaches that any act which is intrinsically evil cannot be moral, regardless of circumstance or intention. Unnatural sex acts (e.g. oral sex, anal sex, manipulative sex) are intrinsically evil and therefore cannot become moral by being combined with, preceded by, or followed by, a moral act of natural marital relations.
Now there are many ‘teachers’ in the Church who are teaching the exact opposite idea, but they have no explanation for how an act that is intrinsically evil can become good by being combined with another act. As an analogy, bank robbery is immoral, and it does not become moral by being combined with or followed by the act of donating the money to charity.
here is my lengthly explanation of this principle:
catholicplanet.com/CCSE/marriage-sins.htm
May marriage be honorable in every way, and may the marriage bed be immaculate.
For God will judge fornicators and adulterers. (Hebrews 13:4).