Cheated by my Boy friend how to file a case

Hi, I m facing a brutal days in my life. I was into a relationship with my Team Lead and we both were enjoying our company. After a while few situations has been observed and came to know that he allege girls and without knowing them he uses them after he losts interest he will insult or leave her on the way she is. I have come to know this by disguising myself as another girl and started chatting with him. As I was feeling guilty and few other situations I couldn't carry that drama but we have come to know about his intentions how is he interested in having sex with girl whom he dont know and didn't even met her. Unfortunately the proofs we are being hacked and lost. I have said him that I have come to know about your character and have the proofs hence I said him to change. For few days he was fine with me but after January he started misbehaving with me and professionally he is depriving me by not letting my hike and spreading nonsense about me to everyone. Also mentioning that I am doing bad against him and the worst part is I love him so much and want to be with him he is breaking into pieces through mentally and also spoiling my life professionally. I didnt say him anything till date but still he is saying that I m blackmailing instead I have given chances to change himself. On this basis i went to his home and spoke to his parents and the reaction was so cold. Now he is having someone else in his life. I have thought that I need to teach him a lesson that he cannot play with feelings of girls and use them for his needs. I request everyone to guide me so that I can stop his activities and how to move a head legally.