Possibly triggering

So when I was younger (5-7years old (from what I remember anyway)) my brother (3 years older than me) started touching me inappropriately, which at the time I didn't know that it was, this eventually led to him putting his penis inside me but at first I would scream to much. He did eventually go in and out multiple times but as I was so young some parts are fuzzy. I know the basic rape part but is that classed as rape or just harassment?

I've never told anyone this, hence why I'm posting anonymously, and I think it's time that I told someone as I've punished myself with self harm and eating disorders and other things for long enough. Mainly to get it off my chest but so I maybe tell my boyfriend and I could get him to feel less guilty everytime we start something and I freak out on him, he beats himself up thinking it's his fault and that he caused me to have a panic attack because he got caught up in the moment (which also just to clarify with this part always asks even if he wanted to take my shirt off) . I think him understanding would be easier on both of us. However getting it out there feels so terrifying and even writing this gives me horrible anxiety and I want to tell my parents but how? I still live with my brother and I have to pretend everything is fine. What happens if I do tell them, will I be believed?

Being believed is something that scares me because I tried to tell them once before but didn't say it was my brother and they didn't believe me.

And let's say I did tell them and they believed me what would would happen?

Main question: If I told my parents, what would happen?