Cheating case

HI. My age is 25 years and I was in a serious relationship with a guy who is three years younger to me since 2017 January (1year). He agreed for marriage and spoke with his mother as well. She asked to wait till his studies get over. Last month I came to know that he was cheating on me. He took an amount of 25,000 from me last November,2017. Now when I am asking for it he is telling that he will not give and started blackmailing me that he has nude pics of mine and will ruin my life. I went to his office and told his mother all this. He got angry and came to my house and told my parents that I am torturing him a lot and lied that I keep sending him pics of mine. I stay in hostel and hence did not know he was with some one else. He cheated me and now not returning my money. His mother is scolding me that it is my mistake of behaving in this manner. She is telling how can a girl to that extent of having sex with his son. My parents scolded him very badly and I promised that I will never repeat this mistake again. But two weeks back he has put my contact number in a whatsapp group which has guys sharing porn videos from various countries. He nor his mother are not picking up calls now. How should I proceed on this? Please help me