Since this is interfering with your life then you should tell your doctor and therapist. Since you can get into character easy maybe you can use this in a positive way and do some acting in school plays or join a theater group. The more you pay attention to the thoughts the more they bother you, so notice they're there and let them be. Don't try to analyze or change them and eventually they'll calm down. Speak with your doctor and good luck for the rest of the school year. I have a daughter who started high school this year.