Flashblacks

Hello so last spring I was raped by a close friend. It hasn't really bothered me since november but about a month ago he was released from jail. Recent when my boyfriend and I are doing anything remotely sexual or even just making out I have flashback to when I was raped. Tonight I had a flashback so bad that I freaked out and yelled at my boyfriend because I though we was th other other guy for a moment. I am scared I am going to hurt my boyfriend. Does anyone have any suggestions on how to not freak out on him.