Seymour, as you told someone just a couple of days ago, pain and fusion do not have a direct correlation. Some people are surprised to find they have fusion because they've never had pain, and some people never fuse despite severe pain.
Pain can come from other reasons besides inflammation. Stress can cause pain. Stress can cause your muscles to tighten up, which will cause pain. It's also possible that stress can cause pain by affecting brain chemicals. And as we've said before, stress can cause you to be more aware of pain that was always there but not noticed as much.
You're about the age of my children, so forgive me for going mama bear on you, but you really, really need to get a handle on your anxiety. You are going to literally make yourself sick if you don't get it under control, and I don't think you can do it by yourself at this point. Ask your rheumatologist or your primary to give you a referral. Depression is an organic condition, not a character weakness. There are medications that can help. Whether medication would help in your case is something only a qualified medical professional can tell you. They can also teach you how to deal with with the stress and anxiety so that it doesn't make you sick.
Ginny - 58 year old female
Dx with USpA in March 2013; changed to AS in July 2015
Iritis and Scleritis, both currently in remission
unicompartmental knee replacements: right-June 2014, left-Aug 2018
MTX, Humira, Cyclobenzaprine, plus Celebrex as needed
Supplements: Folic Acid, Vitamin A, Vitamin D, Calcium, Fish Oil, Culturelle probiotic, Melatonin (as needed)