Should I break up with him or wait it out? ?

Ive been dating this guy for a month but before we dated he had a "crush" on a friend of mine. She said she didnt like him and turned him down so he moved on. Then at grad after i broke up with my ex we danced and sumething happened. I admitted I had always had a crush on him and he said the same. So of course things never work out. At his b-day party the girl he formerly liked filled me in saying he still had a crush on her but liked me more....so I decided to tell him to wait. I realized it was stupiid and we went out. But lately ive been gone and hes been hanging out with that girl alot. They're also going to the same high school where as Im going to a differnent one. Im afraid he may break up with me for her....should u break up with him or wait it out to see if he does it to me?