My mom doesn't believe me...

I was raped 4 years ago. I didn't tell anyone until last year. I felt that it was my fault and someone was punishing me. When I told my mom she was sympathetic at first but after my second counselling session ( she made me go) She said that I was lying. I asked her why she said this and her reply was " you probably were just sleeping around and are asking for an excuse" I have no clue what to say or do. WILL SOMEONE PLEASE HELP??????