I'm Exhausted!

Somebody PLEASE tell me how some women manage to work 40+ hours a week and take care of their families at the same time??? Ever since I've been in school, it is an uphill battle for me to stay up until 8:30! I can get by on about 9 hours of sleep a night, but in order to be absolutely happy and rested, I need about 12. Honestly, that was the hardest part about becoming a mother, giving up sleep.
My house is an absolute mess, and Isaac is eating chicken nuggets for the third time this week. There are no clean towels, and the ironing basket is overflowing with about 3 times as many clothes as it was designed for. A strange odor is emanating from the downstairs bathroom. The ants in Isaac's ant farm have perished for lack of food and water.
For a long time I thought maybe my fatigue was because I was out of shape, so I started an exercise program. Since February, I've gone to Curves at least 3 days a week, as well as consulted a nutritionist. While it's easier for me to take a few flights of steps, I have not noticed any other benefits (hardly any weight loss to speak of, although my cholesterol dropped by almost 30 points). I'm feel more tired now than I did BEFORE I started working out.
So I had my thyroid checked. Everything came back fine.
I think I'm doomed to exist on coffee and Mountain Dew. Thank GOD it's FRIDAY! And to all those women who manage to have it all - I stand in awe.