Oops, didn't see your post but looks like we were thinking the same thing.
Sorry to take up space with three comments. Good Luck, mamak27.
Hypothyroid checklist. You should see your doctor to rule this out.
http://thyroid.about.com/cs/basics_starthere/a/hypochecklist.htm
Have you had your thyroid checked? Those are some of the symptoms of hypothyroidism.
Sounds like to me you need to have your thyroid checked. Problems with thyroid glands can cause all the symptoms you described, poor sleeping patterns, constipation, hair loss, mild to extreme fatigue and changes in appetite and mood. THe headaches are probably a secondary symptom due to lack of sleep and appetitie changes. Hope this helps. Good luck.