@NancyNC2020 I know that sick feeling you describe exactly. Exactly. I remember it so so clearly.
Like you, my abuser was a bully. She hated me (or seemed to) then liked me but sometimes drafted in her friends to bully me. I was only 6 and wanted her to like me. I don't remember too many specific memories of the bullying, I just remember the feeling of being utterly miserable and crying when I had to visit that house and they hid from me or 'teased' me. The abuse however is crystal clear as it felt so wrong.
Dillo, I'm sure you don't mean to, but I'm sorry but I feel like you are minimising this. I do know what you mean about 'weird' things that children can do but if OP's abuse was along the lines of mine, there were absolutely no grey areas. It was sexual abuse. My abuser knew exactly what she was doing and what she forced me to do. As an adult, I am utterly horrified. Even at that age I knew that it was wrong. God knows where she got it from though. 
Children are capable of horrific things (and I know that this is very often due to being abused themselves.)
Don't want to go into detail but the abuse I suffered was definitely sexual, definitely not just kids messing about and was truly horrendous. I still remember the hot tears on my face and the feeling of being utterly powerless and dirty and ashamed.
I think having your own children really makes you reevaluate things. Therapy may be an option. It's something I've considered but have never been brave enough to do. I just don't want to open that box in my head really. It's there but I don't think about it often and can safely push it away when it occasionally appears. Until today, I've never breathed a word on MN about it until your post OP. Don't know why. It's a horrible little secret that I'm really not sure how to tackle.
Sorry for the essay!!!
Finally, OP, it really wasn't your fault. Your feelings are absolutely valid. There's a whole raft of issues here, not least that as the abuser was a child, this is so much more complicated than 'sexual abuser = evil.' as happens with adult abusers. Child-on-child is such a taboo, emotive subject.
Big hug for you love. 