Shari,
I am 40 too and my husband moved out in May.
Today and the next week or so will be the hardest. Leave room for yourself to feel ecstatic about your life re-opening, for that is what is really happening here.
About depression? PPD isn't uncommon and it isn't our "fault", and other types of depression also seem to serve a purpose. Congratulate yourself for seeking the help you need. Then check this out and look at the section on evolutionary biological hypotheses of depression, and stop castigating yourself for having been depressed:
http://www.billdoll.com/dir/health/q/depression_cure.html
Your husband holds sole responsibility for his decision to move out. That's not on you, so go ahead and make a list of the ways you contributed to the failings of the marriage, but then forgive yourself and keep going...
Make a list of why you loved him.
Make a list of what you deserve in relationship.
Make a list of what you can do while husband-less.
Make a list of your strengths.
Make a list of what you want for your children.
Make a list of the best, most joyous, most memorable moments of your LIFE.
Even low on cashflow, you can still afford a paper journal. Go get one and write in it CONSTANTLY.
Call your friends, current and old. Call your mom. Call your brothers and sisters. Get someone over to your house to help distract the kids with LOVE.
Don't worry about whether he is coming back. Sign up for AAA membership; get a cellphone and put $100 of prepaid minutes on it; get a car charger for your cellphone; put your AAA card in the glovebox.
Live as though your life has always been your own, and all choices yours to make.
He might not come back. You might get divorced. That's sticky and not fun but it is also not the end of the world. In fact it is a beginning.
You are going to be fine. You may find yourself feeling strangely elated. Go with that.
Above all, BE LOVE. I don't mean grovel or beg or pacify or compromise. Just BE LOVE. You will know it when you experience it, and it's good.
I am also the child of divorced parents and so is he and I never imagined he would opt to make this happen in our daughter's childhood. The worst pain I have felt throughout my situation has been FOR HER. I wonder if that is true for most separated/divorced moms.
I do have to say a bit meanly here, your husband is pretty LAME, to leave wife and children just ahead of Thanksgiving and Christmas. Not respectable at all.
You and the children are going to be fine. The transitions are hard and difficult to explain to kids, but YOU ARE GOING TO BE JUST FINE. Challenging times ahead, but also, rewarding. Your lives are re-opening, and the best times are on their way.
I send you love and love and love and calm. Cry it out as much as you need to and EXERCISE when the mood strikes. Anything you do physically to strengthen your body in this time will also strengthen your soul and fortify your spirit. Take care of your body and take care of your boys, and send me a message anytime; I will write back at length.
You are going to be fine. I know it doesn't feel like it exactly, but, leave room for that golden shining light to blaze through and touch you. It is like a wild bird: feed it consistently and it will come more and more frequently to you.
Blessings upon your house and family,
Kristen