Hey ladies!

I have a serious issue.

My guy best friend and I used to date ( 2 years ) We broke it off bcuz I lost physical feeling for him and started to have an emotional affection for my older sisters best friend( 18 ) and I'm 17. After we broke up I found out my sisters friend was going to college this year ( September) and I would still be at home. So for a year we had a fling or a relationship. I don't actually know what it was But now that he's 5 hours away. He didn't put an effort with anything unless its sexual. Even when he comes home it's a sexual based relationship and I liked that when he was home but am uncertain when he's at college. Therefore I turn to my ex who's also my best friend for comfort. Our friendship is turning back into a relationship and I don't know what to do bcuz I may hurt him again. What should I do?