Harrasment and abusement by ex boy friend

If my ex boy friend is harassing me sending the messages and chats to my brother and black mailing me that he will create bad.Ia m tortured ever day by his messages. To escape i said that iam in relationship with my friend now he is started torturing him to he is using me every day and he said all the chats to my friend and my brother, he always uses fake whats app account and he started our relationship by creating fake facebook account, he is a software developer he tries to hack every information about me . moreover i was in relationship only for 2 months we never met each other, we used to talk only over chat and whats app call. I never loved him he tortured me to say yes to him and he started harassing me by saying that iam in relationship with my friend. If iam online my friend is online he will get a pop up and texts me and abuses me by saying im talking to him and loving my friend. He always black mails me by saying that he will show the chats Want an advice? What i need to do