I would look at another rheumatologist again. A woman might be better - no guarantee, but my experience of multiple male consultants has demonstrated dismissal of women.
I have AS and multiple shitty AI conditions.
The gold standard is the MRI. The other stuff is not enough to tell you you don't have it.
The MRI should be a STIR MRI. They look for active inflammation in the spine. The sacroiliac area is key. It's often the primary target of AS. I have evidence of bone erosion there even when no active inflammation. I have however had this for 25 years.
If you're taking naproxen or any anti inflammatory, you want to be clear of it for at least a week before your MRI. It's really frustrating that you can suffer so much and a scan might not show everything.
There are many medication options available. Many private consultants would refer you to NHS treatment on diagnosis.
Exercise, movement and heat are important. Naproxen is helpful, yet use PPIs to protect stomach.
I also have EDS. I wonder if some people have just that. It can cause lots of issues that cause pain and more yet it isn't an inflammatory immune mechanism and therefore inflammation won't show up.
In your position, I'd get the cash together to see the best you can. I've unfortunately had to do this many times and spent thousands. I am however allowed access to the best medications on the NHS.