I need you ladies thoughts and opinions on something!

My best friend and I love each other and care a lot for each other, our feelings are mutual as we've discussed them. Here comes the puzzling part in my opinion, he doesn't want to have sex with me. We've fooled around but won't go as far as intercourse. I've asked several times what's up with that, his answer is always the same, he sees me as more than just a piece of ass and although he'd love to have sex with me he doesn't want to screw up what we have right now (our relationship is almost perfect) as he says sex changed things. I respect and love his answer but a girl has needs!! Idk what to do to convince him that our whole world won't come crashing down if we have sex.