Relationship confusion?

hello im 15 years old. i used to go out with this boy, and then i left him because it just did not feel right and there was a 2 year age gap that made me nervous.However recently he got back with the girl he was with before me and him got together. Imogen(his girlfriend) is lovely and although she lives far away, its obvious she really loves him. I asked him the other day, if me and him could still be mates, despite what has happened between us. He said not unless he can be my friend with a privileges( he means he still wants us to be able to kiss etc). I said no because he has a girlfriend. He then blocked me on MSN. Last night though, he asked me again and i sad no again. This time though he spouted off a lot of silly love phrases that made me give in and say okay. I feel really bad because this means he will be cheating on his girlfriend and i wish i hadn't been so weak...ive let him get his own way. Yet i love him so why deny us being together. im so confused as to what to do. Please give me advice...x