Be very, very, VERY sure of your facts. You obviously have some things you are basing your suspicion on. A hunch is not a fact.
Follow these steps:
- Tell her that you have a very serious matter to discuss with her to get her attention.
- Prepare for a stormy and heated discussion. Either way, you are going to hack her off and you may also become cross.
- Ask her directly if she slept with X. Tell her why you are asking the question and lay out all your evidence.
- Depending on her temperament, her answer will be either positive and defiant or negative and deeply, tearfully disappointed in you that you could think this.
- Believe her, whatever her answer is.
- If her answer was no, apologise, beg for forgiveness and start building up the trust in your relationship. You just shattered it.
- If her answer was yes, carefully decide if this is a deal breaker for your relationship or not. Will you continue in an open relationship, will you forgive her and try again, or ask her why she did it and if there is a need that you are not fulfilling for her. Some soul searching for both of you lie ahead.
- If you don’t believe her, your relationship is over anyway and you must break up with her – now.
Follow her. Especially if you know her typical routine, when something changes even the slightest, be there to see why. Its not easy but thats one way.
Hire a private investigator. That’s expensive though.
If she did it once and isnt cheating now, you may never find out.
Sucks you have this problem. Hopefully you are just being paranoid, but if your gut is telling you, listen to it and act on it to know for sure.
Ask her if she says yes she did then you have your answer if she says no she didn’t then you have your answer.
Ask the suspected guy, see above.
If it’s something that happened before you and her got together then what does it matter if they have or haven’t.
If it’s something you suspect has happened deceitfuly while you have been together and you don’t believe either of them maybe you should think about your future together, because there are some problems with trust.
Well, there are two possibilities. Either you already have some reason to believe she’s slept with another guy, in which case what more proof do need? Or you have no reason to think she’s slept with another guy and you’re being being suspicious and controlling, in which case you are being a bad boyfriend, and she’ll be better off without you