That's right, you have NO IDEA. You're just assuming you were getting sufficient calories and I hate to break it to you luv, but looking at your symptoms (low body temp, tired all the time, losing hair, easily sick, heavy periods, weak and atrophying muscles, high TSH), those are all classic signs of starvation. You're simply under-eating and you're exactly why I'm asking the Webmaster to rename the AF support section to "Starvation Fatigue".
Be happy about this though. Now you know what has been causing your problems.
Also want to mention, in case you were doing it to, over-exercising is another very big problem around here, which is another way to calorie-restrict. Most women here have been under-eating and over-exercising in their obsession to be and stay thin. Just ask Faith110, who thought it was her raw vegan low-fat diet that was making her fall apart even though I tried to tell her many times over that she simply wasn't eating enough.