This is complete torture, i dont know what to do anymore. help?

I have a problem where i am verrrrry self concious of my looks/appearance. I dont mean to sound superficial and shallow but i was extremely teased when i was younger so it has changed and affected who i am today, and unfortunately not in a good way. I am a 17 year old girl now, and i think if i do something bad in life something bad is going to happen to me right after, like im going to get fat/ugly. I know it sounds crazy but i can't help it and it really worries me because I think its true and its going to happen. Im very gullible and worry constantly what others think of me. I hate it, i never used to be this way. I used to have many friends, i was well liked, I was a fun person and I would go out all the time. I never worried about things like this, but its starting to get worse to the point I just give up, Im sick and tired. I can't go on dates, have relationships, etc. I dont know what to do.... how am i ever going to get on and move on with my life like everyone else?