I'm terribly sorry to learn of the death of your son. You may very well be correct that your husband is dealing with unresolved grief (or guilt) regarding your recent loss. [Please understand that I include guilt only because this is a very common emotion among parents who have lost children... I do not mean to imply anything else from that statement.]
You may wish to consider reading:
BEYOND TEARS: Living after losing a child (by Mitchell)
THE GRIEVING GARDEN: Living with the death of a child (by Redfern & Gilbert)
LIFE AFTER THE DEATH OF MY SON: What I'm Learning (Apple)
...even providing these books, just laying around the house or next to the bed, might prompt your husband to look at them.
Beyond unresolved guilt, your husband may be suffering from depression. Research has consistently demonstrated that treatment plus medication is more effective than medication alone or treatment alone for depression and/or anxiety. Further research has shown that Cognitive Behavioral Therapy (CBT) is the most effective form of psychological treatment/intervention - particularly in dealing with mood disorders (like depression).
It is likely important to differentiate if your husband is suffering from unresolved or complicated grief (which may well be the case) or Major Depression. The treatment for Major Depression is often quite different than it is for grief. A licensed mental health professional (lmhp) would be able to help with that process. This could be done individually or as a couple (or even a family).
In the event that your husband is diagnosed with Major Depression, a licensed psychologist/psychotherapist with specific training in CBT modalities would be able to address your concerns. I would encourage you to find a licensed mental health professional with whom to work, employing CBT. Be sure when you speak to a possible licensed mental health professional that s/he employs CBT techniques - not just "influences from CBT" or "an eclectic approach."
With regard to medical treatment, many/most physicians appear to begin with a Selective Serotonin Reuptake Inhibitor (SSRI) to treat depression. Because I am not an MD, it is beyond my purview to address medication concerns, however.
If this matter is truly one of profound grief, I would urge you to contact a local bereavement center that specializes in the needs of grieving families. Even if your husband does not agree to participate, it will allow you to better understand your own feelings and to cope with his. If nothing else, *YOU* may wish to consider speaking with someone directly to deal with your husband's pain. I believe there is a grief center in the UK located at:
Now, being in the US, this particular Yank has never contacted them before... so I provide this resource as an uninformed observer... perhaps they can direct you to more assistance or be of immediate help.
Once again, I wish you and your entire family all of the best.
* FEEDBACK ENCOURAGED. Please contact me prior to leaving negative feedback so that we can resolve the matter. I am eager to work with all JA clients to provide them with useful/helpful answers. Thanks again.