Was he after one last fling or what? Does he really love me or not? LONG but please help....?

This is far too long for people to read (except for me because I'm a chump), so you won't get any answers this way. Anyway it sounds to me like you both enjoy the drama of not being together even if you want to be together, and it also sounds like he wants to have his cake and eat it too. Does he love you? To some degree of course, you were his first, you'll always have a special bond together, but if he really loved you then you would both be together. Does he just want a fling with you? Well he shagged you whilst he has a girlfriend, is it really not that obvious? Although I doubt very much it was 'one last' fling as you put it, he'll be back for more sooner or later. He's a 20 year old guy, he probably doesn't even know what he wants. As long as he can sleep with you when he wants, and stay with his girlfriend, I doubt he's going to make an effort to be in a relationship with you. A friend of mine who is 25 recently fell in love with a 19 year old girl from his university, and of course being a teenager at Uni, this girl just wants to have fun really, and my friend wants to be in a relationship with her so much, and she likes him and is sleeping with him, but doesn't want anything serious. I guess you could say the same for your situation, you're both young and even if he does love you maybe he just wants to sew his oats. He has a girlfriend so I think you should move on with your life.