The Catechism says:
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, if not even reduce to a minimum, moral culpability.
It says clearly that "masturbation is an intrinsically and gravely disordered action."... It is a mortal sin... One can not receive Communion after Masturbation, he needs to go to Confession before Communion... However some priests say you can receive communion after Masturbation without prior Confession!, which seems to me wrong, according to the official teachings of the Church in the Catechism.
See my commentary on Masturbation
The Catechism says:
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. Basing itself on Sacred Scripture, which presents homosexual acts as acts of grave depravity,140 tradition has always declared that "homosexual acts are intrinsically disordered."141 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 homosexual tendencies is not negligible. This inclination, which is objectively dirordered, 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.
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.
Homosexual acts are mortal sins, though homosexual orientation is not a sin.
See my commentary on Homosexuality-Sodomy
The Catechism says:
2354 Pornography consists in removing real or simulated sexual acts from the intimacy of the partners, in order to display them deliberately to third parties. It offends against chastity because it perverts the conjugal act, the intimate giving of spouses to each other. It does grave injury to the dignity of its participants (actors, vendors, the public), since each one becomes an object of base pleasure and illicit profit for others. It immerses all who are involved in the illusion of a fantasy world. It is a grave offense. Civil authorities should prevent the production and distribution of pornographic materials... It is a mortal sin.