What do I do if boy has cheated me, taken money and is blackmailing me

I am 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 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 didnot know he was with some one else. He cheated me and now not returning my money. His mom is scoldingme that it ismy 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.He shared my number in a porn whatsapp group3weeksbac.plzhelp