Am I not good enough to marry?

I love my boyfriend. I love him to death. The only problem is that he does want to commit. Or rather, he's commited to me but not really commited to me. What do I mean? Well, I'll explain.

Den and I have been dating for five years now exclusively and yet, he won't propose. Hell, he won't even talk about our future together.When I question him about why he won't propose, he gives me one of the following lovely responses:

1. It's not on his list of goals.
2. I can't force him to do anything until he's good and ready cause he's a man and men make their own decisions.
3. Why ruin what we have now by doing something crazy like get married ?
4. We go on trips and I buy you stuff, isn't that enough?
5. Why are you being so materialistic? (when I ask about getting an engagement ring)

Friends say I should leave him because he's never gonna take the plunge and marry me, that he'll just keep messing with my head forever.I love him a lot but part of me also thinks I've gotten too comfortable being in a relationship and I'm scared of being alone.I just get tired of feeling like he's only wants me around because it's convenient and safe and he's just waiting around until he finds someone better.

My self esteem is screwed up enough as it is without having seeds of self-doubt planted in my head.Is he with me bcause he can't find anyone else? Is he just settling? Am I good enough to fool around with,but not good enough to marry?Is that what this all comes down to, being that girl he fools around with but not the one he spends the rest of his life with?