My husband and I don't have a physical relationship

Why not talk to him? If you're getting nowhere, then why not try a marital therapist or counseling of some sort with a member of the clergy or even someone who is trustworthy, neutral and that possibly knows you both?

Why ask a bunch of strange people on the Internet who don't know you and might be in the same situation (or worse) than you? If this has gone on this long, as frustrating as it sounds, in part you have had a responsibility to speak up more assertively...as you've let it go this long while you're unhappy.

A solution to your marital problems lies in having a dialogue between you two so why not work together to come up with a workable solution? It sounds like your not happy..and that your at the end of your rope. It's time you both work on a solution to this seriously and in unison, if you can.

Incidentally, his having a picture of a breast on his computer is not a sign of cheating. It could be a sign of anything at all. at least, he's still interested in sex. there's nothing about which you wrote that should make you suspicious of him cheating on you. Suspicion can lead to unnecessary paranoia.

Birdlady people change. You two are not the same people as you were twenty five years ago. Some folks cheat when intimacy exits a marriage. Some do not. Do you know the answer you are searching for, and are not confronting?