I can’t stop thinking about my rapist(s) sexually

I was sexually assaulted June 2017 by two guys. It was the hardest thing I’ve gone through but with therapy, a great boyfriend, and close friends I’ve been able to get past it and find peace/heal.

Now, a year and a half later (it’s still crazy to me that it’s been this long) I can’t stop thinking about them in a sexual way(like when I masturbate or sometimes have sex with my boyfriend). What the fuck is wrong with me!? I feel so disgusting and dirty and messed up in the head. I mean I’ve heard about a few instances where this happens but why me!? Why now after all this time!?

I need some advice please. I’m disgusted with myself