I was d 6 months ago right before my birthday. What should I do?

I'm 15 right now and still a virgin besides what happened. I don't know what to do. My parents are divorced (I am adopted too) and my new stepdad d me. My mom found out and she told me that if I told anyone she will press charges on me for slander (she is a lawyer). So I can't tell the police. I have no family to move with either and my dad and I don't get along well. I'm sorry, I feel so stupid for asking but I just have no clue what I should do. Plz help me. Is there any way I can still press charges on him? Will there be evidence left?