Move on. You're being dumb. HE just told you if nothing better comes along, he'll settle for you, just so he can have sex with you. Since you told him, the only way you'll sleep with him is if you are in a relationship.
Your scenario has BAD IDEA written all over it.
IF you want to get screwed over, dumped, or cheated on, then by all means, patiently wait, cross your fingers, and Hope that he doesn't find a better girl to screw.
It doesn't sound like he's crushing on you or wanting as you as much as you want him. If he was really into you, he'd be jumping onto the idea of actually being with you. When you like someone a lot you want them! You don't tell them "we'll see" if they ask for more. No person in love would do that. Move on girl.
Don't get him back. It seems that he's just using you as a friends with benefits without any option of getting back with you.
he sounds like a girl with all that "i don't know what I want!" crap
Scroll Down to Read Other Opinions
What's Your Opinion? Sign Up Now!
Sexual Relationships 
Sexual Health 
Most Helpful Girls