I believe that you are sincere in your questions. That being said, I would invite you to look at the “fruits” of “simple fornication in a relationship with good friends”. Let’s look at them: abortion, (even partial-birth abortions!), wounded souls from destructive casual sexual encounters, STDs (herpes, clamydia, HIV increasing exponentially) artificial birth control, rampant homosexuality ("same-sex marriages??), divorce, destroyed families–especially the children, unwed mothers, teenagers having babies, and the list goes on. How could anyone consider this to be healthy? God meant for sex to be pleasurable, but this is reserved only for married couples. This is a privilege. Despite the claims of the intelligensia we are not 98% chimpanzees! There is a whole other 2% unaccounted for–at least scientifically. But, in genetics that is a monumental difference.
If you are a "catholic through and through, you would be better served engaging in a good, solid Catholic moral theology or Catholic theology class. Ask a good priest to recommend one to you. There are some excellent books written by very CATHOLIC authors who have written many books on moral theology. Try also reading some of the papal encyclicals on human life (Humanae Vita), and others.