Even if it ends up NOT being ankylosing spondylitis exactly - you should know that there are some hereditary factors that predispose to AS but also to other, similar conditions which are collectively called “inflammatory spondyloarthropathies.” Given your brother’s diagnosis you probably have a higher chance of one of these conditions because of your shared genetics. So yeah absolutely ask another physician until someone investigates your symptoms!
+1 for Winix. I’ve had several of the 5500-2 units for 2-3 years now. They do a good job and I appreciate that they have HEPA + charcoal filters so eliminates more than just particulates. My main complaint is that the lights don’t fully turn off at night so I always have to cover them with something (usually a T-shirt). Otherwise I really like them.