The fatigue until your medication levels are correct is incredible. If your TSH is coming back normal range, but you're still seeing the fatigue, ask to test FreeT4 and FreeT3 to determine if you need a T3 supplement in addition to T4.
Yes, this is so key. I lost 7 years of my life, laying in bed, due to not being properly diagnosed by a few doctors, that I NEED T3. One doctor even told me it was all in my head.

I need T3 more than I need T4, as my thyroid just doesn't make any.
You might have to shop around and find another doctor who will put you on T3. Not all of them really look at the Reverse T3 and
Free T3, is is the most important T3 level, as it indicates how much Free T3 is in your body, not metabolized properly.
I joined thyroid groups who taught me to find a naturopath who does integrative medicine over just a plain endo. He immediately took me off of Synthroid, and put me completely on a compounded T3 Sustained Release formula which my pharmacy compounds.
I was warned it would take quite a while to feel the effects. After 3 months, he upped the dosage. In 6 months, he added on Armour Thyroid, which is a natural mix of T4 and some T3. And he slowly upped the dosage of both until I was at the max I could be for both for me. He also added a natural desiccated thyroid supplement I get from the health food store. As I still needed extra thyroid support.
I do not take all 3 at the same time. I have heart arrhythmia if I do. So I have to space out the drugs. (it's actually better for my energy level.) I take Armour in the morning, the desiccated thyroid supplement a few hours later. It works like crack cocaine, I can feel the boost in energy within a half hour. Then just before my energy starts dipping a few hours later, I take the T3 Sustained Release. I have energy for a whole day that way.
He also put me on a regimen of 50,000 iu of Vit D, iron as I was so anemic, also Vit B, magnesium and selenium, as I was so depleted of
everything.
In the beginning, I would have some energy, and then start doing too much, as I needed to make up for all the time I lost. I'd end up energetically crashing, laying in bed again for several days. He told me I just have to go S.L.O.W. and have patience.
It took another
3 years to finally feel whole, strong and normal again and strong enough to even work overtime. Last year, I even pushed myself at work, volunteering for extra overtime hours, just to test and see how much I could work and do stuff before I would crash. 7 straight days with overtime hours was my limit. Which is a LOT, considering at the beginning with this doctor I barely worked a 4 hour day, then crawled into bed and slept for close to 16 hours. Then barely have enough energy to work 4 hours the next day. I worked overtime several weeks last summer and fall.
I have my life back.

Last year, when I told my doctor I never thought I'd get here, he was surprised. He said, "Why did you question it?"
I said, "Because it took so long to get here."
Just know it will happen, but you might have to shop around and find the right doctor for YOU. And it may take time.