Is sex a good idea? A really cliched question that really needs an answer.

Ok. So... I'm 15 and turning 16 in November. Girlfriends turning 17 in April. We started dating just over a year ago. Not too long ago (maybe a week) she told me she wants to have sex. The horn dog side of me immediately took over and agreed. But since then I've been having some doubts, and for a few reasons. One is that she lives a good 600 miles away. We were dating a little while while (8 months) before she was sent to a boarding school. Another obvious one is our age. Also, my family is catholic and expects me to maintain abstinence until marriage. I have never particularly agreed with this subject but have followed my families wishes. I also have reason to believe that before I met her she was raped (she has asked me 3 or 4 times what I would do if she was and I found out. A few days ago she also said something happened before she met me, that it was no big deal, and that she was still a virgin. This scares me but I said I believed her). I know this shouldn't bear too much of a reason as to sleeping with her or not, but I want to lose my virginity with someone, not to someone. Finally, the physical risks scare me quite a bit too. I don't want either of us catching an STD or becoming parents at this age. She's been on a birth control pill for awhile now and I own condoms. Basically, I need some advice. Any good ideas?