Bullying has indeed shaped your character. However, that is not your personality. You are born with your personality (shy, social, etc.) That in itself is neither good or bad, since all personalities can be either good or bad. It's what you do with the personality you have that shapes your character.
Ideally, when you were first bullied you could have reacted differently, and things might have turned out differently. However, all that is past, and you can't change the past. .
You seem to have a good idea of how you became who you are. Remember, you and only you are in control of your character. You also seem to realize that it's not what you would like to be, and it's certainly not fair to people you meet who haven't harmed you. So now you have the job of changing your character so you are more accepting of other people. You can get counselling, read self help books, and/or do a lot of soul searching (and praying if that's your thing). Everyone has past problems to overcome--it's how we overcome them that define who we are.