Advice: opinions please

Amber
Okay I'll try to just hit the key points, but I would like another opinion. I am currently seeing a guy. We have known each other for 12 years. We met when we were 12 and started dating at 15. He literally was my first everything and I experienced so much with him. We broke up right before college because we wanted to experience life without each other. I'd say a year later we ran into each other and the rest was history. Needless to say we still weren't there yet. So we don't have any contact for three years. During that three years I fall in love with myself and a new guy but he was too young. May of last year me and my high school sweatheart link back up and it's like we never left each other's side. The day we graduated high school he told my parents he wanted to marry me. I didn't really think much of it because we were young still are in my opinion. We're both 23 and he is still tells me he wants to marry me. My problem is I don't know that I want to marry him. I can totally see my life with him and us having children. We've been talking for a year and a half now and we both say we're single. I have told him before that I want more and he made a valid point. We are both still pretty young and still live with our parents, I'm still in school and neither one of us are in a place to give our all to the other. He works a lot and it bothers me. Also I can be  super affectionate and he's not. What do you guys think? What should I do?