unless it was helping your pain... but, like with so many
OTC meds, Advil is another famouos
OTC med that triggers migraines and causes rebound headaches, it could have also been the cause of the original pain or it could have been amplifying the pain if it was also temporarily removing it at night.
So, it would be a good idea to cut back on the Tylenol PM in the hopes of reducing it until you were not taking it at all anymore, then you might find that your headaches go away entirely.