For obsessive thoughts an OCD med could help, such as Prozac or Luvox. Though given you are Bipolar maybe they could be stemming from mania and in that case a mood stabilizer may be better. You've got ADHD too, hmm. I don't have ADHD but they once tried Guanfacine for me because I couldn't focus due to intrusive thoughts. Guanfacine ended up making me hyper so I had to go off it but it likely wouldn't do that to someone with ADHD. Hard to say what the best thing to try first would be but I think you have options. Like TicTacGo said therapy may be helpful too. Also, you said past events. Are they traumatic events? If so you may want to try some PTSD treatment, whether it be therapy or meds.