I'm sorry you're struggling like this. (hugs) thyroid can be frustrating huh?
Not sure whether this is of any help but when my levels are off, I have more trouble handling stress then I used too. it makes sense, really, if the engine ain't working properly a car wont drive smoothly either. Because of having less energy, things can more easy be overwhelming. I know realizing that ain't helping in order to solve it of course.
As far as managing stress goes, kinda depends on what works for the person. Maybe some stress reliefs techniques such as yoga can help? Try to be kind to yourself, most of the time we're not by far as harsh on others as we are on yourself. When you're doing your best, it's good enough. What would you say to a friend in the same situation? say that too yourself.
Sometimes stress can be caused by the conflict between what we feel we should do and what we can do. It's about the distinction between what we feel we should
and what we actually have to do and can do.
Please keep in mind things will get better. i know it's hard to miss out on family events you want to attend yet don't feel up to attending. In my story, I had to miss out on some weddings, first communions, in short events a person just cannot catch up on, yet I could not, I really was not physically able to attend. Not only did I feel bad (if not I would have been able to attend), I noticed I felt several unnecessary emotions too, the latter one only made things worse. Point being, I know it's hard, but try not to stress over it. Again you're doing the best you can!
Hang in there and hugs!