Have you been living with a cheater? Have you left a cheater? Then you are dealing with the aftermath. Thats a state of hopelessness and turmoil. Because you are probably dealing with a lot of questions where you cannot find answers for.
Why did he or she cheat on me?
Is he or she happier with this other person?
Is there a chance of winning the partner back?
Should I reconcile with him or her?
Should I move on without?
All these questions and more will regulate constantly in ones head and lot of books will be read about solutions to get the relationship back on track or what to do. The best thing to do is ofcourse find a counselor. Go into counseling. Because you need some outside help. And not from a friend or family member but someone who is not invested in your relationship. Someone that is totally neutral. A stranger so to speak. Ofcourse that cost money but doesnot necessarily be expensive. It will be worthed.