I've done lots of regretful things?

Im 13 turning 14 this year. Ive done lots of things in my life that im not very proud of. Theres lots of things that i did that really emberassed me and ruined my image. I know i should have thought of it before i do things but im those kind of people who just do something and then realise what they have done wrong after. I just cant help it cause thats who i am. People call me retard because i always do stupid things. Will this ruin my life? What do i do to stop this from happening? I know i should think through everything im going to do but everytime i do that things come out wrong. I know that people do mistakes but i do mine almost everyday! Its stupid! I really need help! What do i do?? Thank you :)