Why do I keep having these nightmares? I need them to stop!?

Well obviously the reason of the nightmares is your ex, do you miss him? That might be the reason. I think what MIGHT help is for you to go somewhere else, like go on vacation with a friend or family member, or hang out with friends, or maybe even get a new boyfriend. What seems fun and exciting to you, give it a try. (: Good luck.