AS as a secondary inflammatory arthritis diagnosis?

Hi, I have a sero-negative inflammatory arthritis diagnosis, I'm on methotrexate since October up to 17.5m injection. Has anyone else had AS as a secondary Dx? MTX has been amazing for my legs, ankles, hands and arms BUT My shoulders, neck, backside and lower back are still very painful, and my back sounds like a bag of cornflakes being rolled over when i bend/turn. I'm back with rheum soon, i'm going to ask about AS so am hoping you can offer some support on what specifics to cover to make sure i'm reassured? I've mentioned the butt, back & neck pain consistently and they haven't offered MRI etc.