Flashbacks. I don't know how to handle it and I need help😭

About a half year ago I was sexually assaulted by the boy I was talking to. My boyfriend of almost a year knows everything that happened and is very good at handling me when I have my moments. Nobody knows except him because one day when I was giving him head he pushed down on my back and held my head down and I started crying and screaming for him to please stop so I knew I had to tell him at that point. He also knows to be sure I'm okay before he sticks his hand down my pants and sometimes I just can't do it bc I can still hear the other boy saying "stop moving my hand. Let me do it!" How do I get past this? I can't handle the flashbacks when me and my boyfriend do stuff and I don't feel like its fair to him... he's always the one that makes me stop and he comforts me the best he can when I feel like i need to keep going to please him unlike the other boy. I have bad dreams about what happened still. Please help me