love or lonely?

I have a very good friend that is a guy, when I met him I was in a long distance relationship with my high school boyfriend. Right after graduation, and before parting ways "temporarily" my then boyfriend gave me a promise ring and asked me to wait for him. After 6 months of not seeing him on a daily basis the relationship ended and things with my guy friend started to get more physical. From the start, we both made it clear that we were only interested in each other for sex but meanwhile we just became closer and closer. We party together quite a bit, and twice he asked me to marry him but I obviously didn't feel ready for that at all. I didn't even take him seriously truth be told. Neither of us are perfect, we each come with plenty of emotional baggage, him more than me mostly because he's 8 years older than me, he's 29 and I'm 21. He also fathered a kid that he didn't tell me about til like 2 months ago, but when I did the math I realized he knocked this girl up at about the time that we started sleeping together. He's not a huge part of his 10 month old sons life, he pays child support and visits once or twice a month I think. He isn't super comfortable talking about it, especially with me. And I have no reason to be mad, I mean we weren't in a relationship and I was sleeping/dating other guys casually too. To this day though the two of us hangout and talk a lot. We confide in each other a lot, he's called me crying as have I him. We're completely comfortable with one another. We help one another out financially when things get tight. But just as much as we get along we argue. We get jealous of each other a lot too. Basically we are dating and have been for what will be 2 years in October but he's not willing to commit, which I guess shouldn't be a problem considering our original agreement, but it is for me. Things have changed so much for both of us and when it comes down to it he's the best thing in my life. And I KNOW I'm all he's got to rely on. I don't know where "being with" him puts me as far as having a real relationship with anyone else though. Obviously I can't have one as long as he's in my life, but every time I try and cool it down with this guy friend of mine, he gets all sad that I want to "breakup" with him and promises to be better. So I take him back and for 2, or 3 weeks tops, things will be great but slowly by slowly his life will become more and more self centered until I feel like I'm forcing him to do something he doesn't want to, and when I try to talk with him he'll get distant which he will of course blame on work (he works in retail), and then once I stop coming to him he'll beg for my forgiveness, which starts the whole cycle over. I'm only 21, it seems WAY too young for me to be playing this game! I don't know what to do. How can I make this guy see that we could be great together? He also previously lived with a girl for 5 years until she cheated on him, so I think he's afraid I'll do the same. Considering that when we started out flirting and fooling around I already had another boyfriend maybe he has a valid fear, so how do I make him understand that he can trust me?