Sounds to me that you might need your dose increasing, are you due a test? Just make sure they check the Free T4 and T3 as well as TSH.
I used to feel like that, have brain fog and could not physically talk, almost like an unwinding toy. Made my face ache and when I did speak, I sounded slurred.
It will make you feel very sleepy.
It might also be sleep apnoea. I was diagnosed a couple of years ago, they reckon I have always had it but had gone undetected. it is normally associated with being overweight, but please note, I am not implying you are overweight so do not take offence, as that is not what I meant - basically you don't have to be overweight to have it. It could be several reasons why a person might have it. I know a firefighter that has it even. But the symptoms can be the same. Do you suffer with disturbed sleep problems??
There is also a chance that you might be anaemic or have a B12 deficiency as they go hand in hand with thyroid symptoms as well.
Let us know how you get on and hope you get the sleep and your energy back.