Well if you're sure that he's not with you just because you're pretty, which you seem to suggest he's not in your question, then it's something unexplainable for him.

Sometimes there's just a connection between people and it draws them towards each other. Regardless of what they have or don't have, that crap really doesn't matter sometimes. Sometimes as in rarely these days. Rarely as in love is almost lost these days, and people only want someone for personal gain. Perhaps this is one of those rare moments, where two people love each other because they do, because they feel it, because they're human and have strong emotions for each other for mostly illogical reasons.

Perhaps he just loves you for reasons he can't even explain. Personally I think you should be open and honest and discuss this with him. He clearly knows who you are. As far as not being worthy, nonsense...for him, you offer everything. And that is to have you by his side, to be there. Because he loves you and wants to take care of you. Stuff like that. I doubt he expects anything from you.

Or at least, in my opinion.

ask him. hes the one that knows