Decisions on Sex

My boyfriend and I have been together for a little over half a year now and lately things have been heating up fairly quickly. He's brought up having sex a few times but I've always said no because I wanted to wait til we were 18 and I could get the birth control. But lately I've been having doubts as to whether or not I can wait that long. I've become extremely ambivalent over the matter and i don't really know what to do. I'm not sure when it's best to do it, and we're both still virgins…I just don't really know