Hi, and welcome (I'm glad you spell your name Stacy, not Stacey, as we have a Stacey here already!!
I hope you are going to get treatment for your own heath problems - I believe underactive thyroid is realatively easily treatable, ie, it's a question of getting the dosage of (thyroxine?) correct, to compensate for the level your thyroid is not producing the 'activity' hormones that its function is. You may find it a bit 'fiddly' as the doc ups or lowers the level until it's just right for you.
That said, of course, even if you are back to full functioning, you still have the problem of being a carer. I know FM is a wretched condition, because the cause is so poorly understood, and treatment is so 'inadequate'. My niece has it and it can be very variable in tis impact - some days are fine, some are bedbound. Wretched.
How incapacitated is your husband. I'm possibly going to sound a little 'unsympathetic' here, but please ensure you don't do too much for him! It's easy for 'invalids' to become very practically and, worse, emotionally and psychologically, dependent on their carers, and you must do the very least you can for him.
Is he off work permanently? I do hope not!
PS - my niece takes 'legal canabis' sometimes which she's found really helps. Supplies are slighty tricky to find - you need a good source and that isnt' always easy.