Did you know that if you have Hoshimoto's, you are more likely to have other auto-immune disorders?
I swear, I have lived what you are going through right now. My chest pain wasn't so bad as long as my Synthroid was right, but recently it is been getting worse along with a lot of other things. That's another story.
I guess my first question to you is have you tired the actual Synthroid name brand drug? I was on levothyroxin initially, and didn't get very good results. I switched to synthroid, and my life has been much better. My symptoms really improved after that.
Maybe that is an option... Good luck and Good Health!