Yep, sounds like it could be thyroid. You can also experience memory loss, weight gain, cold flashes, and a feeling of just not with it or a lost, spacey feeling.
My thyroid issues were discovered at age 11. I complained to my mom about having a sore throat. She noticed my lower neck had a lump in it. It took a year of testing until I was finally diagnosed with Hashimoto's. Our family physician kept reading the test results and saying my TSH and the other hormone (can't remember the exact name, it's a T3 test) was normal. But, my thyroid was huge. He finally sent the results to an endocrinologist, who read my levels for what they should be for a child and they were off. The endo. diagnosed my thyroid problems as being due to an intolerance to iodine. (I have to watch my iodine intake, little iodized salt, etc)
I should have been huge because of the hypothyroid, but I was skin and bones as a child. The doc also discovered I had a goiter on my thyroid which kept my metabolism pumping all the time, never slowed down. I ate like a horse, but was very physically active too.
I have been on meds since I was 12 (40 now) and will always be. Periodically my thyroid "trips out" and I have to adjust my dosage.