Start jiujitsu, judo, or another full contact martial art and stick with it. If you don't stop this bullying now it will continue in one form or another for your entire life. The time will pass anyway, why not improve yourself, make many friends and toughen up? Hopefully you live in an area with bjj schools, you can usually speak with whomever it is that runs the school, explain your situation, and get some advice without a hard sell contract. Please note that this is not a recommendation to train to confront your bully, this will instead lead you on a good path to true self confidence and knowledge of your own strengths and weaknesses. Don't worry about looking foolish, everyone does at the start, just stick with it and go to at least twice a week, you'll be amazed by how fast your life will improve. I'm happy to help you evaluate bjj schools in your area if you'd like. You're a lot stronger than you think you are!