Boys..

I've been friends with my boyfriend for almost 2 years and we've been together for 9 months. He means the entire world to me and I know he's the man I was to marry. Only thing is, I know and have no problem admitting that I'm not ready for a relationship that leads to that commitment at this time. I'm younger than him so he's very much ready for marriage and kids but I'm not. I was to mingle and still go through my wild teen stage. I was forced to grow up fast and I finally let myself be young for a bit then got into such a serious relationship. It was comforting at first but now it's scary. I know I want to be with him but not at this time. I also have this guy that's been my best friend for a year and a half now, he was actually the first guy I ever did anything with and I was the first girl for him (I lost my virginity to my current bf though). This best friend confessed his feelings for me about a month or so ago and he lets me know how much he at least wants a chance to be with me because he thinks he could make me happier. I tell him the stuff girls usually tell their girl friends about their relationships so he knows the things my bf does to irk me and that hurt my feelings. I do care so much for him and given the chance a year ago I'd be with him. What should I do?