Have you asked family or friends if they've noticed any difference in your husband?
He may be in the early stages of Alzheimer's/dementia.
Or, does he have a waterworks infection, as that can lead to all sorts of problems with what is going on in his head?!
And here comes the untasteful part, and I am so sorry, but do you think he may be having or considering an affair? If he is distracted by another woman, maybe someone who has been friendly - not necessarily meaning anything by it - he may be taking that as a sign that she is interested!!
But please ask family and friends if they've noticed anything strange about him, and do not assume I am correct about an affair as I could be (am hoping I'm) so wrong, but as it entered my mind I'm sure others have thought it, too!
Good luck.