Actually mainstream clinical research which has been peer-reviewed and published in medical/psychological journals agree that it is impossible to change your sexual orientation and attempting to do so is damaging. See: American Psychological Association.
Not according to those on and off CAF who have in fact discarded those previous “orientations” (otherwise known as lifestyles

). Unless we should conclude that they are liars, which would not only be uncharitable but terribly arrogant of any one of us to assume.
Believing that it can be changed is actually against Church teaching, as the Church teaches that it is natural and intrinsic.
No. The Church teaches that the causes are unknowable. Please do not misstate Church teaching
2357 Homosexuality refers to relations between men or between women who experience an exclusive or predominant sexual attraction toward persons of the same sex. It has taken a great variety of forms through the centuries and in different cultures.
Its psychological genesis remains largely unexplained [nothing in there about “unchanging,” “natural,” or “intrinsic”. Basing itself on Sacred Scripture, which presents homosexual acts as acts of grave depravity,141 tradition has always declared that "homosexual acts are intrinsically disordered."142 They are contrary to the natural law. They close the sexual act to the gift of life. They do not proceed from a genuine affective and sexual complementarity. Under no circumstances can they be approved.
2358 The number of men and women who have **
deep-seated =/= ‘intrinsic’]homosexual tendencies is not negligible. This
inclination [nothing about “natural” in there], which is objectively disordered, constitutes for most of them a trial. They must be accepted with respect, compassion, and sensitivity. Every sign of unjust discrimination in their regard should be avoided. These persons are called to fulfill God’s will in their lives and, if they are Christians, to unite to the sacrifice of the Lord’s Cross the difficulties they may encounter from
their condition [nothing in there about “natural” or “intrinsic”]
2359 Homosexual persons are called to chastity. By the virtues of self-mastery that teach them inner freedom, at times by the support of disinterested friendship, by prayer and sacramental grace, they can and should gradually and resolutely approach Christian perfection.