First thing you need to understand is that this is a serious problem. It's very common that couples stop having sex, but it's also very common for people to be in unhappy relationships that leads to divorces and just plain misery.
I don't know why, but it feels like demanding or wanting sex is a relatively small and petty thing, compare to other forms of intimacy and affection - I mean, if you were refused a hug or a listening ear or a shoulder to cry on, you would act angry and upset way before a full year gone by, right? Sex is an important to our relationships and feeling of togetherness and emotional well being as a hug or a talk.
Also, it's important to understand that this is not (just) your problem, even if you are the one wanting the sex and he doesn't. This is a mutual problem that should be solved together. I suggest an open talk about it, not late at night, in bed when you ask for sex and he refuse, but set a time, let your husband know you want to talk cause something between the two of you feels bad for you and explain that it is very important for you that the two of you go back to having sex.
If he agrees, I think it'll be a good idea to talk to a couple therapist or a sexologist.
My guess is that in his grief, he replace the role of his mother in his life (helping,supporting, nurturing, unconditionally accepting, pure) with you and so now, it's much easier for him to get into a comforting style of relationship then a sexual one. A hug doesn't require him to prove his masculinity or make an effort to give in a sexual way.