My personal belief is that if we define ourselves by our problems we are less likely to overcome them. In my view you are a 37 year old with 3 kids, who tragically lost her son, has had many other challenges to overcome and happens to have clinical depression. You are not the sum of your challenges and you have made a great step forward by coming here for support and seeking medical advise. Does your doctor know that your withdrawal is so severe? If not, call him/her. Withdrawl is usual but does not have to be so severe.
Grief is individual and different for everyone. Your feelings of loss are valid and you own them. It is okay to feel sad and all the other things you must be feeling. Give yourself time to grieve, only you will know what is the right amount of time. I am sorry for your loss.
Keep coming here because we are here and we do understand.