I am with you, sister. I was painfully shy and didn't fit in with the kids who seemed to know how to act, talk and handle themselves in social situations (or so I thought- they were probably just as insecure, but I couldn't see that.)
As kids and teens, we were really just learning day after day after day new things, bombarded by choices,stuck in awkward situations and trying to make sense of it all using our teenage brains- which are hardly the most stable, predictable, sensible things!
I don't think you purposefully chose to let people mistreat you since you were just a kid (or a teen or even a young college kid) and it is really hard to think on your feet without some experience behind you. I didn't realize I'd been mistreated or made-fun of at the time, just in hindsight. So, I have had to forgive myself- I didn't know any better, seriously. And I eventually stopped holding a grudge against the "mean kids" because they were only working with the skills they had (and several actually had MEAN MOMS who I new, so that made sense that they didn't know how to treat others in a caring, compassionate way if Mom was a jerk to others around her!)
But, the good that has come out of it: I know how to better help my kids manage the challenging years ahead, can share some of my experiences in hopes that they won't feel as awkward or -gasp- ever try to bully someone themselves!! (Not accepted in this house!!) I tell them everyday how we are all unique and different and isn't that wonderful? And they think, "yeah, that is cool." I have a mild hearing loss and auditory processing challenges. They know to turn to me to let me read their lips if we are outdoors or it is loud. I point out often, "This is how I am built" and how they are unique "allergies", "blue eyes", "missing 6 teeth at once" (my 2nd grader.)
I only wish everyone saw the beauty and the benefits of difference!
So, hopefully, one day, my little guys will be as caring as adults as your sweet 4 year old will grow to be!