Disclaimer: For those that don't know, Kevlarhead is a dad. This may influence your interpretation of his advice, and explains why he's shit scared of posting on a sex thread...
"You might like to offer him some tlc without sex, eg a massage. Show him that you are still interested in him, even if sex is off the agenda for the moment."
"Making an effort to regain some sense of the person you were before may help."
I'd suggest your DH is, as he says, seeing you as a mum and as nothing else. Yes, you are a mum, but that doesn't obliterate the rest of you. Problem is he's seeing the mom role you play, and veering off from it.
Would it be possible to drop the mom role, and (like the other posters have suggested) try getting back to the way things were, if only temporarily?
I'd avoid anything overtly about 'sex'; can you both get dressed up and go out somewhere for a few hours? Or (if you can't get out) both put on some non-sick stained clothes and watch a film or something? If you make sure there's a wee corner of your life where you don't have to act the mom, it might help stop him thinking of you as solely a mom.