I was similar as a child Fuzzy, and I'm 'too' quiet and anxious also now. I'be not been abused, but I can relate to those other things.
What you could do is trying not to care about what certain people say or think about you. I know well that it's difficult But we can do it. Only the opinion of the people who love us is important.
And...you aren't stupid!!! You're awesome Love you!