Sexual abuse

So basically I’m 18 now and I’ve started remembering things I did as a child that I’m starting to realize we’re really wrong. I remember me and a friend when we were really young like 8 &9 or 9&10 basically showing our private parts and doing oral to each other. I remember us both just being super nonchalant about it and I remember her always wanting me to do it to her. It didn’t happen a lot but it did happen a few times. I feel very guilty now because now that I’m an adult I feel very responsible for what happened because she was a year younger. I remember being sexually abused by my older brother when we were kids but I know he was abused too so I never blamed him I’ve always loved him and still do to this day. I remember always being afraid of this man my parents were friends with and every time he’d come over I would hide under the table or under a blanket and I wouldn’t come out because I was terrified of him and I’m starting to think it was due to abuse however I don’t remember it ever happening. My cousin told me she was abused by our grandpa and I don’t remember it happening to myself but now I don’t know anymore. I feel Very guilty about things that happened when I was a kid and now I’m depressed and think about suicide more now that I’m able to understand the depth of my childhood. I don’t let my boyfriend go down on me because I feel so disgusted and it bothers me when he does so I never let it happen. Can someone give me their insight and possible advice?