If I was you I would stay single and carry on having fun, because you cant like these guys that much, else your friend is right, you would only like one, and you would really know if he was right, you just know when you click with someone, it isnt all about the looks. As for the ex...maybe best to tell him where he stands, find out where you stand and firmly say you either are together or you arnt, you sound like you still like him, but he sounds like he likes you, but perhaps is playing you for a bit of a fool. If you are going to stay just friends dont let him come to uni, it will make things worse. Find out where you stand with him first, then go man hunting