How to control thoughts?

My mind is taking over. My story has been posted a million times. Ex ended things after 6 years and now he wants to fix it. We broke up at the beginning of May and he told me he wants to work on things a week ago. My mind races, over analyzes, worries about the future, if I will get hurt again, if he's talking to girls. He assured me many times that he isn't talking to anyone and why would he if we are working things out. I have read 5-7 self help books and controlling the mind. I just can't seem to control it and stop assuming the worst