One of the sharpest ways to destroy a relationship is suspicion.
Sure, someone might say they are going to the gas station but wind up at a supermarket, or claim they are going to buy shoes and come back with a hat. But that doesn’t make them a ‘suspect’ or a ‘liar’.
Being suspicious of annoys people beyond speech. If they are cheating, it angers them. If they are not cheating, it angers them.
Simply put, if you have suspicions, keep them under control Don’t let them know.
The moment one feels spied upon their response is to withdraw and escape.