What to do with my ex boyfriend/ current fling?

So I have been with my ex boyfriend for almost 3 years...throughout our relationship we took a break for 5 months but always hung out and talked throughout the break..we've been back together since last december (2010)...when we started talking he didnt treat me that great..hung up on me..still texted girls he talked to while we were on our break..he took some other girl to prom while we were talking and bought a rose for her when he asked her to the prom..he danced with girls at his prom..i was lenient because i knew it was his prom..these are the bad things that happened..overall he treats me right and we have our good times..he still hasnt asked me to be his girlfriend yet and we've been talking for almost 7 months since we broke up and act like a couple..he calls me every morning..we talk every night..see each other most of every day..hang out on the weekends (sometimes) i just dont know what to do because he starts his freshman year in college this august and ill be a sophomore in college..we're both going to the same college..i just dont want to waste my time..he still hasnt asked me to be his gf after everything we've been through..i just dont know what to do..i feel like he might just blow me off when he starts college and i dont want him cheating on me and meeting new ppl in college while im there...its just all confusing..i dont know what to do..