I feel your pain. Recently, my issues of fatigue and exhaustion were made more clear by the revelation that I have hypothyroidism. Medication has made all the difference in the world to me, and I hope you are able to find a solution to your own issue.
As a personal trainer, I would look at your situation (mentioned in your post) and encourage you to have 3 goals for the first month:
1) Get at least 8 hours of sleep (throw in an afternoon catnap if you can, too).
2) Adjust your diet: cut out sugar, eat a large no-carb salad meal for supper (no eating after 7:00 pm, if possible), and drink at least 2 quarts of water per day. I keep a quart jar in my kitchen window filled with water, a visual reminder for me to take a sip here and there throughout the day.
3) Exercise at least 15 minutes per day (mandatory). I recommend Peggy Brill's The Core Program. This program will help you eliminate daily aches and pains, all while helping you begin at your fitness level.
If you can get these things going, it would help you by the second month to add walking to your daily routine (at least 3-5 times per week). If you can't get out to walk, I highly recommend Leslie Sansone's walking workouts in DVD. These are great for every fitness level.
Try to cut out any unnecessary daily activities that stress or push you too much. Streamline and simplify your housekeeping and cooking. Monitor outside of the home activities and stop doing too much.
Hope you begin to feel better!
Blessings.