Do you and your husband have children? How long has been depressed?
Try your best to get him into counselling. Be involved and go with him, physically take him to the therapist if need be. As hard as this is on you, right now he needs you to be the "parent" here and because of that it will change your dynamic with him for a while. I know it sucks and it isn't what you bargained for, but sadly these are the cards you've been dealt with.
He needs to be on meds, so hopefully with the help of counselling they can find a drug that works well with him and doesn't have bad side effects.
You also should do counselling as well, it'll help you cope with this and deal with him better.
Hope this helps.