If there are no other problems in your marriage, and no other changes, then it may be that he’s telling you the truth — the ring is bothering his finger! I think that what you really need to do is to ask him straight up if there’s anything bothering him in the relationship that would cause him to want to take his ring off and appear to be single to others who don’t know him that well.
Men wearing wedding bands is a relatively newer fashion, so if the men in his family aren’t ring wearers he may not see anything wrong with taking the ring off.
If it’s really bothering you, you can ask him if he’d wear a more comfortable ring, and make an occasion for the two of you to buy him a ring that’s a lot slimmer and more with what’s called a “comfort band” fit.
Otherwise, since there doesn’t really seem to be trouble in paradise — just a shedding of jewelry — I wouldn’t think too much more about the significance of his not wearing the ring. If he acts married to you that’s infinitely more important than what he wears.
