It's been a while since you posted, just curious to know how you're doing?
I have a few ideas for you about your thyroid levels.
One thing that could cause you to be hypothyroid with all the low thyroid symptoms while still having a low TSH is fluoride. Fluoride takes the place of Iodine in the building of thyroid hormone, giving you all the symptoms without an elevated TSH. This is what happened to me. It turns out, unfortunately, that green tea and black tea are very high in fluoride. You can read my story somewhere on cure zone if you're interested, so I won't rewrite the whole thing here, but just wanted to let you know if you are a tea drinker, you might consider stopping to see if that helps.
Bromine and chlorine are two more halogens which do the same thing that fluoride does, replacing Iodine in the body, since all of them are in the same group in the periodic table, and have the same valence electrons (yay 9th grade physical science), they can fill the same receptors in the body. If you're a swimmer, or own a hot tub, you are probably exposed to one or both in large amounts.
Illnesses can also lower TSH while keeping T3 and T4 low, according to studies I've read. But this is not likely your scenario since you've had symptoms for months/years.
A low thyroid causes absorption problems and low stomach acid. If you have had symptoms of low thyroid for years, you likely also have nutritional deficiencies. It would be a good idea to add digestive enzymes and an HCI supplement to each meal, as well as supplemental B12 in methylcobalmin form and Vitamin A from fish oil (not betacarotene) which are two things every hypothyroid person is deficient in, and which then contribute to the low thyroid cycle.