So what does the Catholic Church teach about abortion, pornography, homosexuality, artificial contraception, masturbation, etc.? During the period following the 1960’s many priests and bishops became their own Popes and dispensed advice to Catholics which was based on the false premise that said “Let your own conscience be your guide”. That would be like going to see the doctor and asking what you should do about cancer, and having the doctor say – “Let your own conscience be your guide”. That doctor would rightly be called a quack. If we are all going to let our conscience be our guide concerning sin, that means that 5 billion people on the planet can have 5 billion different set of rules to follow, and that would be chaos.
Why did Jesus promise to send the Holy Spirit to guide the Church in Truth (John 16:13) if every individual can become his/her own infallible source of moral theology? Jesus founded a teaching Church to do just that for us. For priests and bishops to abdicate their teaching responsibilities for whatever reason (to be liked by their parishioners?) and to tell their parishioners that whatever they come up with in their mind is OK is heresy. The Church has seen a great drop-off in the number of attendees at Sunday Mass, and this is the reason why. If my conscience is going to be my guide, then why do I need the Church anyway?
The Church has a Catechism, which is the official teaching of The Church. It is a product derived from sacred scripture, sacred Tradition, and the Magesterium. It has been approved by Pope John Paul II, one of the greatest men to ever live. No Catholic who wants to be in good standing with the Church and its head, Jesus Christ (Ephesians 5:23), has the right to make up his/her own personal theology. Those kind of people would be called heretics. The Catholic Church is an all encompassing way of life. It’s not open to picking and choosing some of this and rejecting some of that. Every household has rules for their kids, and good parents don’t let their kids decide on their own which rules they will follow, i.e., when they will go to bed (midnight on school nights), or what they should eat (ice cream every day). The Catholic Church is no different (Matthew 18:3), because the Holy Catholic Church is a FAMILY, God's Family! Having a personal relationship with Jesus is great, but not at the expense of The Truth taught by His Church! Salvation is not "me and God" alone, apart from His Church that He founded.
To answer the original questions concerning Church teachings, here are the answers, linked back to the Catechism for your reference.
Abortion – 2271 - Since the first century the Church has affirmed the moral evil of every procured abortion. This teaching has not changed and remains unchangeable. Direct abortion, that is to say, abortion willed either as an end or a means, is gravely contrary to the moral law:
You shall not kill the embryo by abortion and shall not cause the newborn to perish.
God, the Lord of life, has entrusted to men the noble mission of safeguarding life, and men must carry it out in a manner worthy of themselves. Life must be protected with the utmost care from the moment of conception: abortion and infanticide are abominable crimes.
Pornography – 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.
Homosexuality – 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, tradition has always declared that "homosexual acts are intrinsically disordered." 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.
Artificial Contraception – 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. 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:
Thus the innate language that expresses the total reciprocal self-giving of husband and wife is overlaid, through contraception, by an objectively contradictory language, namely, that of not giving oneself totally to the other. This leads not only to a positive refusal to be open to life but also to a falsification of the inner truth of conjugal love, which is called upon to give itself in personal totality. . . . The difference, both anthropological and moral, between contraception and recourse to the rhythm of the cycle . . . involves in the final analysis two irreconcilable concepts of the human person and of human sexuality.
Masturbation -- 2352- By masturbation is to be understood the deliberate stimulation of the genital organs in order to derive sexual pleasure. "Both the Magesterium 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." "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."
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.