I Was Given Percocet 10 For Migraines A Week Ago'

I was given Percocet 10 for migraines a week ago' but after taking one at the first sign of migraine attack getting ready to become really bad and again the second day still having headache problems I took one and again one after 6 hours. now 5 days later i'm still feeling awful even though Percocet helped. how long before this stuff to get out of my system?