I've Been On Prescription NORCO For Over A Year. 1

I've been on prescription NORCO for over a year. 1 tablet every 6 he's as needed. Last week at my regular doctor appointment I was asked to take a urine test. I have also had migraines for at least a year, which I was just prescribed the Rx RIZATRIPTAN. On the Lab Order, she wrote Drug of Abuse panel, then under assessments, 346.00 Migraine with Aura.
The Norco is 325mg for chronic pain.
first' I'm concerned about "drug abuse" statement (I haven't), next are the migraine headaches related to the Norco? Also, the Rx for migraines worked wonderfully, but my Insurance only pays for 9 pills every 26 days... Why?