Maybe the symptoms of stress, but more like the symptoms of boredom with you. It happens all over the world, everyday of the week, every minute of the day...men get bored with their OH/wives. I suppose it is all to do with the biological function of the sexes,females to bear and look after the offspring and males to propagate and maintain the species.
What should you do?
AB females have got a poor track record for advice...Rooney, Giggs,Crouch to name but a few, when advising to get rid of the "offending partner."
In practical terms there are only two choices that you have, tell him to go and leave you OR accept the status quo.
The decision is yours and yours alone.