while you seem to be mature for your age, and your boyfriend also seems mature, understand a few things;
1: birth control is not 100%. you can use the pill, and a diaphram, and he can use a condom, and you can still get pregnant.
2: sex is a big step in any couples life. be absolutely sure that you are ready for any emotional changes that will occur.
3: recognize that us guys, especially the younger ones, tend to like to talk about our conquests, even if we dont instigate them, so there is a very real possibility that you will get a reputation that you dont want.
4: guys do tend to get jealous and possessive as well, and we have a bit of a time letting go of the women we love. so be careful that you dont end up with an ex boyfriend who is a stalker, stalkers do harm the ones they stalk.
5: some guys get it into their heads that all women want them after they have had sex, so dont be surprised if he starts chasing other girls afterwards.
6: some guys put on a front where they seem to be taking their time, and not pressuring a girl for sex, when that is part of their plan. when they get what they want, they move onto the next girl, especially at that age.
i would discourage you from having sex at your age. it would be better for you to wait until you are 18, and in a long term relationship before you take this step. too many young women take this step before they are truly ready, and regret is later. i dont want you to be one of these women. also dont forget your parents in this equation. what is their reaction going to be when they find out you are having sex? especially your fathers. remember your decision affects more than just you and your boyfriend.