A husband who murders his age peer wife because he needs to get rid of her in order to marry a young woman is a typical plot in Agatha Christie's stories. The young woman was typically a secretary or a governess. Times have changed drastically since then and your husband does not need to murder you if he decides to go off with a young woman. Plus, there doesn't even seem to be a particular young woman on his mind: he just lusts after your women in general. He can easily continue doing that with you by his side.

We cannot say what irrational desires he might be harboring, though.