Is he still working three jobs? Are there other factors that could lower his libido? If so, I expect he just hasn't got the energy for that kind of stuff and his body has said "whoa, let's get rid of this function for a while". If he says he's never had the urge for sex and he's been doing it for other reasons than sexual attraction (physical enjoyment, because it is expected of him, etc) then he could be asexual but doesn't know it, and that's a suggestion I make not because of the low libido (since asexuals can still have high libidos) but because you said both that he doesn't have the desire and that he sees you as the mother of his children and not a sexual being.