I'm assuming since you're ashamed to say it to him, you know in your heart that he is not cheating on you but are still having some upsetting thoughts regardless. Sometimes it helps to check the. Occasionally it is pretty reasonable to think my boyfriend is doing something suspicious: for example if he is deleting his texts, having less sex with me, coming home later and talking about a female coworker more (all things that I've actually experienced even though he wasn't cheating on me). Based on those details, it's a reasonable conclusion to come to that he's cheating, even if it isn't what's really going on. There's a difference between accusing someone of cheating however vs. saying "i'm struggling with thoughts of you cheating based on some things i've noticed. can you explain them away and/or validate how distressing it is to be feeling like this when I know it's not "logical" or true?". Cause even if in your heart you know it isn't true, you can still feel like he is and that's pretty upsetting!

Then I'm usually able to remind myself "silly brain, trying to make me think my partner is cheating on me. he obviously loves me deeply and cares about my well-being". Or sometimes I'm just able to check the facts and do all this on my own in my head. Maybe that's what you're talking about? If you know that the facts don't match up to even remotely support your thoughts then I wouldn't say it explicitly unless really asked about why I'm acting weird, sad, aloof, distant, etc.