Dearest
I understand your situation.
This situation can be avoided if you have a good relationship with your husband. Maybe there is a lack of communication between you two. COMMUNICATION is the most important factor to be in a healthy relationship.
I suggest you to talk with your husband about this and tell him to open the door between you and the mother-in-law. Or have a decent heart to heart talk with your mother in law - be a friend instead of a daughter-in-law.
Otherwise just stay strong!
You need to make some changes before its too late, and when you say 16yrs you must have done something, but maybe not enough! Get the car moving by putting some petrol in it, otherwise it'll just remain stuck... if you won't its your own fault.
God Bless!