Your nightguard might not be doing enough.
I never had any jaw pain, but all of a sudden, I couldn't
open my mouth very wide. I saw a TMJ specialist and ended up with a MORA (mandibular orthopedic repositioning appliance), which I wore for 7 months 24/7, and now just at night.
If your TM joint is bad, you may need more than a plain nightguard. This special thing I wear actually keeps the jaw pulled down and forward, which "unloads" the TM joint.
I also gave up chewing gum, which made me really sad!!