"If it doesn't feel right to you then it's probably not right for you."
The primary reason one believes their mate is cheating is because they have noticed a change in their behavior which they do not like. Even if you found out your mate was not cheating BUT the behavior remained, odds are you would not jump up for joy,
You don't need someone to cheat on you or abuse you in order to give yourself permission to walk away from a relationship that you are either unhappy with or do not feel appreciated. (Know yourself, Love yourself, and Trust yourself). Trust your instincts. Unless you are some naturally "paranoid" or "insecure" person why doubt yourself? Why would you want to be with someone you don't trust?
The only purpose for trying to "find out" if someone is cheating is for us to (prove) we're not crazy or stupid! To learn we are being cheated on simply gives us an "explanation" for the change in our mate's behavior. It also may offer us a little "ego" satisfaction to "bust them".
Being "unhappy" or no longer feeling you can trust your mate ought to be enough of a reason to move on. You get to (choose) who you spend your time with. Therefore if you are unhappy in a relationship but elect to stay in it then you are (choosing) to be unhappy. (I'm not talking about an isolated moment of unhappiness. I'm referring to a lingering overall feeling that things aren't right.)
Life is short. I have one rule when it comes to relationships. If I'm not happy I don't stay. One man's opinion! :-)