If you get meds from your doctor, and you run out before the refill date, then buy the same from and OP is that
doctor shopping? I bets lots of people already do this, because frequently doctors under-prescibe. Is is against the law?

I'd like to see the actual law pertaining to this stated, if you could find it.

Pain patients have the right to seek appropriate treatment, and I will fight to end for pain patients rights. I guess if you don't want to fight for patients pain rights, then you should suffer?