HELP!!! I have had Graves' Disease and then a thyroidectomy and still extremely tired.?

A couple of months after the thyroidectomy, I came down with mono. That seemed like it took forever to get over. Since then, I feel like I cannot get any strength, tired all the time, muscle weakness, had to have a hysterectomy, then an appendectomy and have recurrent sinus and ear infections and headaches all the time and mood swings like crazy. I have had my hormone levels checks and they came back all in the normal range. My husband makes fun of my feeling tired all the time, but it literally takes everything I have to get up every day and go to work and keep a clean house. All I want to do is sleep, sleeping sometimes on my days off for 12-14 hours a day. The doctors keep uring me that my thyroid levels are "normal" since they found the right dosage of synthroid. I feel caught between a rock and a hard place because the doctors keep telling me I'll feel better if I just exercise, but I am so tired and weak that going up a flight of stairs exhausts me. Does anyone have any suggestions? I have been to several doctors and feel like there is more going on than what they can seem to find.