That's great that your symptoms have been getting better! I really hope this was just a temporary blip that will not be a problem long term. I can see why you'd be anxious by the thought you were developing another serious condition in addition to AS. Whether or not you do actually have a different condition, the anxiety you are feeling in and of itself is can have real effects on how you're feeling physically and certainly makes things tougher mentally/emotionally. Do you have any support system? Some family members or close friends you feel comfortable sharing this anxiety with and working though it together, or even a therapist or counselor? I have obsessive thoughts and anxiety, especially around my medical issues, and have benefitted a lot from talking to a therapist.
On the other side of things, any news on your MRI results?