Im in a sticky situation how can i fix it?

Okay i met my husband and fell in love with him when i was 15. We got married when i was 16. now almost 7 years later we have a beautiful baby boy who is 18 months old. Anyways to make a long story short. After my son was born I was extremely depressed because my husband called me fat blah blah and wasn't emotionally there for me. So I was taking anti depressants and had a little too much to drink one night and ended up cheating on my husband with some one who was very close to his family. Well I couldn't live like that so I told my husband we Split up for a while. When we were split up I continued to talk to the other person because at first I didn't have a job and I needed financial help until I got on my feet and he told me that he felt responsible for what happened. Well we started seeing each other more. But i still loved my husband i told himone night that things were over and that i was going to make things work with my hubby. He got very angry and started to blackmail. (That he would tell my husband that I slept with him while we apart) I ddidn'twant that to happy because i love my husband and family very much. Things are just now starting to get better between me and my hhubby'sfamily again. Im a good person that made a mistake but now im tired of being blackmailed. I just cant take it anymore. It has to stop. The only thing he wants is for me to continue to talk to him, but we fight alot becausehe wants more than that and i feel guilty like im doing something wrong. Any ideas on how to stop it.I just want him to leave me alone. I have not had sex with him since or anything like that but every time Idon't answer the phone he gets mad and starts telling me hes going to tell my husband. I just want to be able to have a happy life with my husband. And it would destroy us if he foud out what happened even though we were seperated.