I don't know what happened to you exactly, but what you describe sounds a lot to me that something DID happend to you. I think it isn't very normal that you can barely remember anything from age 12 and less, particularly as you aren't very far away from it today. For a 70+ person this might be different. @Toller describes it very well what might have happened to you.

To me both starving and overeating are ways to act something out, just like other things you describe. The reason for that could be indeed sexual abuse, but it doesn't have to be necessarily. Any other kind of abuse or trauma can do the same thing for you. I would highly recommend to find a therapist to work on this one as suddenly remembering things from the past can be extremely upsetting and emotional and it would be very helpful if you aren't alone when this happens.