How can I say im gay to my parents?

Ive been having feelings for woman since i was younger but i didnt fully become gay until i hit about 17 now that im 21 and living out on my own im kinda confused on how to come out to my parents...i mean they have said gay jokes or made fun of gay ppl in the past, nothing negative just your regular jokes,and we come from a tough christan background, you know the ones that went to chuch every weekend, me and all my bros and sis were in the choir you know the usual and so on.Both my parents have stated their disaproval about gayness which makes this tougher. the only person in my family that knows is my 18 year lil brother and he loves me just the same which was a good thing. Now im off in college my parents think im living in student apartments down here in fla but really i been living with my gf of 2 years for about 6 months now. this is my first real serious relationship i have had with a girl and i really care about this person and her dad/moms accepts our relationship but im just stumped on how i can explain this to my parents without getting negative reaction.....oh god im so confused help!