My husband says he never, ever suspected I was having an affair. I think some of that was because of a disconnect in our marriage.

I think gut feelings mean something, but not always what we think they mean. You might pick up that your partner is holding something back from you, being secretive, not being honest or open with communication, etc. The information being held back could be something from the long past or something he/she doesn't feel can be discussed with you, but it might not be an affair. I would try to open communication in a non-accusatory way and see what happens.

Mythology abounds in a bad marriage, and that can take it in either direction, sometimes in rapid flip-flops. My wife oscillated between blind ignorance of the obvious to utter nonsense in her suspicions. I'd leave the reactions from your spouse where they are and focus on yourself. Being forced into lying to dispel scary situations does no one any good.

Oh, you are the CS and are wondering if your BS knows?

I think my H suspected plenty of times but chose to ignore it.
And in the thick of my A fog neither he or I really could care less if our spouses suspected. We bragged about our latest lies. (Not proud of it, but it's the way it was)
Affairs do cloud you.....
I'm not sure it's as much paranoia as much it's nearly impossible to cheat for years and years and never raise a red flag.