It's going to come with time. You are going to get fed up of your insecurities and you will start become to more bold.
To speed up the process, I suggest to take risks. Wake up every day with the mantras like...
"I am greater than great."
"I am loved!"
"I am happy!"
"I can do anything I want to!"
"I am superior!"
People will begin to see your confidence and the same people who made fun of you will like you and want to be your friend. I used to be bullied and made fun of in middle school and high school, then I got to college and got bold and successful and those same bullies want to be friends with me now.
You will be happy!