Trying to move away from a emotionally draining relationship

I was in a relationship with my junior for two years. It was fine time during the first year. I did everything from arranging his Birthday Parties to help him out with Projects. But with the second year things started changing. He started getting mad at small things and acting extra possessive. I tried hard to convince him that I was unable to take the shouting. But he said I had to take him the way he was. At last things got worse and I cheated on him with one of my class mates.
I did not want to tell him initially. But I felt really guilty and told him honestly. He acted cool about it and despite some bad time we came back. But after this the relationship got abusive. I finally left my college and told him that we were not meant to be. But he i not ready to accept it. He still keeps calling and even found out things about my present Boy friend.
He keeps telling me that I love him and he loves me and there is no point trying to avoid this fact. He says that he is sorry and at times its like emotional blackmail. Since he was my first bf I can not let him go off easily as well or ignore him completely.
Help me. What should I do?