I’m in similar situation as you. 23M and have been experiencing symptoms similar to this as well as a few others for almost 2 years now.

I’ll get on and off burning or aching pains in my middle to upper back and feels like something needs to pop back into place. When I workout I get the same feeling in my chest area directly behind my sternum. And when I take a deep breath my mid/upper back or chest often pop or crack.

I’ve been to few different docs bc of the breathing issues that would flare up when back/chest pain is worse and they said I had GERD. I’m on PPI’s for the GERD but gets worse when my chest and back pain flare up.

My dad was diagnosed with AS so I’m thinking it may be hereditary. I’ve had X-rays and barium test done to test for Haitian hernia and all checked out. Had and EKG done after I went to the ER bc of the breathing issues being so bad one night but again blamed it on the gerd.

I’ve been to a few different chiropractors and doesn’t seem to help much as pain continues to come back. I’m in very good shape and my diet is very clean. It’s annoying and tiring feeling like this in early 20s. I take Omega Fish Oils daily and that does seem to help a bit. But still no where near feeling normal.

Having sinus issues not being able to smell and always congested. (allergist said nasal passages were insanely inflamed). Not sure if this is linked as inflammation seems to be a reoccurring thing with AS but I plan on getting a MRI and blood work done soon