Honey, look, girl to girl, it's not worth throwing away your youth because of lust. I agree with the whole "sex is a choice and anyone mature enough can make that choice" and in no way am I saying that you're too immature for it, but you're 13. I know people who got pregnant at 12, 13, 14 and so on and they had to give up their teenage years to raise a child. If you're asking these questions then it's clear that you're doubting this. Hold off until you feel like this is something you're completely ready for. Also, birth control and condoms can both be defective. When used together, it's very unlikely you'll get pregnant. If you do decide to do this, make sure the condom brand is a well recommended one and that you take your birth control the same time everyday for at least 2 weeks. But please really think this through.