Doctor Answers (2) on Depression
What you need to do is convince your husband that you're going through a lot of stress and convince him to go for a Couple's therapy session, which can later eveolve into a family therapy. By doing this, the therapist will be able to give an objective point of view to your husband, who will then understand the dynamics of the problem, and would possibly start taking corrective actions.
Another thing you need to get addressed is whether you need treatment for clinical depression/anxiety as a result of the conflictual situation. The same might hold true for your mother in law, who herself might be depressed and as a result, her behavior has been irritable and un healthy for you and the entire family.