lost and in need of help *****Trigger Warning******

So, I've never gotten help for this and I'm not even really sure what to call it, as if it needs a name. In 5th grade (I am now at the end of my freshmen year in college) i was home alone with my best friend and her older brother, who at the time was in 7th grade. He showed us these videos of naked people, I obviosuly know now that it was porn, but before I had never seen anything like it. I just sat there and watched, with my best friend and her older brother, not sure what to think. The next thing I know we leave to go upstairs and he follows. He wants us both to take our pants off and we do it. He wants me to lay on the bed and I do it. He then says hes going to put his thing in my butt that way I don't get pregnant (no, i hadnt had my period yet but i didnt know the difference). That was that. Years later I told my sister and we cried and then it was "forgotten" again. Until recently, it had never come into my mind but a couple times and everytime it did I would get disgusted with myself and push it to the back of my mind again. A few months ago I talked to a girl who had been raped twice. It opened this door for my memory and I can't seem to push it away anymore. The other night in a drunken state I told my best friend about it and had a breakdown. I have no idea how it even came up but it did. I don't understand why it is bothering me all these years later and way I can't get rid of it. Was this rape? Is there a name for it? I dont even know. It makes me feel so alone even when I reached out. I am going to talk to my therpaist once I am home from school but until then, can anyone help me?