Even when you are not swollen, your bones can still be actively changing, and can be very painful.  Maybe you need a second opinion?

Some of the things people say their rheumy told them reminds me that somebody had to finish at the bottom of the class. Swelling might result from inflammation, but doesn't always. Inflammation may result from the fusion process, but also doesn't always. Some joints never swell because they are encapsulated. Hips and the spine are examples of this. But those are the most common joints to be affected by AS.

You can't always see the swelling. I've never had visible swelling but terrible pain.

I've had AS for 14 years lots of fusion, lots of pain and I have never been aware of any swelling.

I am one that knows that eating anything sugary makes my pain worse. I ate a tablespoon of nutella yesterday and I am achy today. Hope u feel better..

I have had pain with and without swelling in my knees. My knees are not my problem at the moment but I have had problems with them in the past. I would go and see another rheumatoligist.

I wish I had an answer. I will give it my best shot from my own experiences.. What happen to you happens to me in similarly only in me the pain was focused in my back at the sacrialiac and top of my
neck along my spine. The swellen and pain comes and then the swellen goes away but pain remains . I think the body adjusts to the pain, and we settle with stiffness. This is why the Dr say that acitivity should be a main focus for us. Keep moving, with rest to a degree where you are trainining or familiarizing what the pain is, and adjusting to it. Because of the stiffness, I try to viusalize a weight has been asserted on me and I must learn to live with the pain. The purpose being that I can then know my limits and try to expand with new muscles that help to adapt to the new bone material.
New nerve endings must be devoped where you pinched ones stop, its an ongoing process like growing. I hope I help make sense of the ordeal. Above all, remain above and embolden your thoughts in the most positive sphere at all times. Good Luck and may the Force be with YOu. :)