Sex? Virginity?

I've been with my boyfriend for 2 years and we haven't had sex. I'm still in highschool, and so is he, and I want to wait until after I'm out of highschool, because I don't want to be a teen mom or anything, but, I kind of want to just have sex now. We're planning on getting engaged this Christmas or somewhere around there. Should I just go for it? How do I approach him about it? Any advice?