When I read your post I knew exactly what you meant about feeling like you are "going around the bend." I was on synthroid for about 7 weeks when I had a similar experience. One doctor said it was a normal byproduct of "coming up" on synthroid and another said it was not?
As for the job you hate, let me tell you a bit of a horrifying story that might make you fall back in love with the job you hate, if only for the benefits. You failed to say if what precipitated your diagnosis was the discovery of nodules and, if so, how many. I am 34 yr old female and they found a single "cold" (you will learn the difference between cold and hot if you don't know already) nodule and, if you ever get thyroid cancer, it normally arrives in the form I have-a single, cold, nodule. I am self employed and had private health through blue cross/blue shield. They dumped me when this started to look like cancer. Everyone that reads this is going to say, in their heads(!), they can't do that. Well, people, before we jump to conclusions you have to go through the permutations of what happens when they try.
I had to write to the state of ct health insurance commissioner who, after 3 months, said what we all knew. They said they "can't" do that. Well, I found myself uninsured with this thing in my neck and, as the state has it's lengthy processes to go through, I had to scramble over the holiday season to find a part-time job that had benies. Now, I am doing fine in business for myself but I have to trot off to this part-time gig all because of this thyroid thing.
Btw, the state said they could not do that and part of my reinstatement was paying for the 3 months I was uninsured, in other words, 1200.00 all so I could get my policy back and then the bills they did not cover when they cancelled me would be paid-all $700.00 worth. In addition, several people warned that they would fish for other reasons to dump me. The moral: stay with the job you hate until they find what is really wrong with you.
The depression and upset, the melancholy, the work outs that get no results, the "new stuff' you are feeling is, I am confident, related to the thyroid. What is a pain in the ass is sorting it all out. Like you hated the job before the thyroid and now, under the guise of thyroid issues, you will start to extricate yourself from it. I would say take a leave if you can because, as you said, food on the table and bills paid is a lot and I could imagine it won't be easy, especially with the freakin' thyroid nonsense to feel 100% to go out and find new income.
I would say go with the devil you know, as my grandmother would have said.
I hope this helps. Write back