You are a fool if you think your lover isn't cheating on you. 

From the moment you trust a person enough to say "I love you" you have placed yourself into the path of potential harm.  To ignore this possibility is folly.   

The wisest thing to do is to never love anyone, or at least never to reveal it.  Remain safe, and alone, and die someday comforted in the knowledge that no one ever put one over on you.  Never say "I love..." to anyone.  

If vulnerability should spill out of your mouth in a moment of weakness, then the next best thing you could do is  pursue damage control.  Don't waste time in ignorance of what everyone else surely already knows (and is no doubt laughing about behind your back.)  Track down the truth until you find it, and then enjoy the reward of Knowing You Were Right.  After all, it is always better to discover bad news than to have it dropped upon you.  That way you remain "the aggressor" and not "the defeated."

Although it is possible to discover that your lover is cheating... it unfortunately is never possible to discover that he or she is NOT cheating.  At best you could only assume this to be true, and at worst you could decide that you "know" this to be true... but you simply cannot know.  Not ever.  Placing this kind of trust into anyone is most unwise.  There is no person incapable of hurting you if given the chance, no matter how you might want to believe otherwise.

It is the most pitiful type of fool who throws caution to the wind and loves another person with unconditional trust. Whether life stretches long or is cut short, whether you somehow make it to the grave untouched by heartbreak or not, you place yourself in the company of unwary idiots when you pretend that nothing can go wrong.  Things can go wrong.  They do go wrong, all the time, to billions of organisms.  

To be in love is to be a fool.  If you should ever find yourself in the most unfortunate position of loving someone, then I am truly sorry for you, but you must make an important decision before it's too late.  Don't be a pussy and switch sides either, commit yourself to a course of action and stick to it not for an hour or a year or for as long as it is convenient or reasonable,... but stick to it to the death,... because trying to have it both ways will fuck shit up not just for you but for the rest of us too. 

Ask yourself: do you want to be Stupid, or do you want to be Right?

And whichever you choose, stand up to it. I'll stand up to it-- I'm Stupid. Always have been, always will be.  It never once bothered me to discover someone cheated on me. I asked for it.  Every time.  

Now you stand up to it, smarty britches. If being Right is important to you, then get the fuck out of the dating pool and die alone,... You're hogging up all us Stupid People's space.