You know, it almost sounds as if your roles have been reversed, and since you spend so much time away from each other, due to your job, maybe you need to get reacquainted with some quality alone time.
Sex is but an expression of other feelings that may have changed, when life has thrown some changes at you. You have to understand, I think, your not as available as you were to him, and its hard to be spontaneous, or even that excited, when you have been absent.
I don't know if he is having an affair, but I do know that the physical love changes, as we age, and it may take more to get the love engine cranked up. ( Okay I'm an older husband, and we don't swing from chandeliers, naked any more)
It really sounds like the communications are just not there, and the adjustments through honest communications is spotty.
Whens the last time you did something fun together??