Hi J., Your posting jumped out at me because I have a 5 year old son in Kindergarten, and work full time as well (and I have a 4 and 2 year old son also). But I don't take the metro, or have the medical issue, so God bless you lady for going going going. HANG IN THERE!!
First, try to streamline, streamline best you can. Read the book ON the metro, not at home to save time if you can. Only give a bath every other day (my son gets a bath 3 times a week, not every night, unless he got sweaty during the day).
Try to take the time (like you have any extra!) on the weekends to make more meals that will get you thru the week. A casserole, lasanga, something you like as leftover so you can just heat it up when you get home. I make pizzas a lot (buy the crust, my 5 year old puts on the sauce and cheese). We have soup with it. I make a bunch of chocolate chips pancakes on Saturday and freeze bags of them (5 in each freezer bag), then pop in teh microwave for about 30 seconds to thaw out, quick breakfast meal.
Is there anyone that can help out once a week? Sometimes just a few hours by yourself (sometimes I go to the grocery store alone) can give you a little breathing room to regroup. How about at your church?
Also, put errands all together, if you go to church, hit the grocery store on the way home. Give your son a few things to do to help you. I just got my 5 year old to start setting the table and emptying the little trash cans around the house. They like to have tasks sometimes.
AND I am a big supporter of a leisurely bath! I take one once a week after my boys go to bed, I read a magazine and just relax and feel a lot better afterwards.
God bless you J.! I'll pray for you to be strengthened and your time to be supernaturally expanded!! --V.