My boyfriend is blackmailing me

Hi, i had a relationship with a guy from last 5year, he was married when he came into relatnshp with me but i was not aware, he has 3kids, i got to know this after 1year, till that time i already had a physical relation with him. He promised after my college complete he will get divorce and marry me. But after that he suddenly changed started abusing me, if i talk to any guy he used to beat me for that stating i have a relatnshp with that guy. He always used to take my money and threat me stating he will tell everything to my parents and he will get my encounter done. and from last 2yrs when i am forcing him to marry me now he started blackmailing me saying he will not divorce his wife and i have to stay like this with him or he will expose me and kill me. In march 2016 he forcefully entered my office premises and took me out to threat me... i called my brother and saved myself. From then he is indirectly trying to threaten me by messaging my family members potraiting a wrong image of mine in front of them...So that i come in pressure and get back to him again. He is playing smartly on one side mailing me very poiltely stating he wants to marry and on the otherhand he is messaging my family members that i am involved with different guys and he can make them talk with those guys. I am in depression because of him, he mentally and physically tortured me, and i cant go out of my house , he still forces me to come back, he was with another girl from last two years promised her also to marry...and side by side from last 2 yrs he is torturing me. I am helpless wht to do now because my family dont support me and he is speaking to them stating he is right and i am wrong.