It could be considered an addiction. Or just a bad habit that you really should avoid. I Googled it, and the Tylenol website that going over the recommended daily dose (2 pills) could result in liver damage.

Have you talked to a doctor about this? Perhaps getting a prescription for a sleeping aid would be better for you in the long run, since most OTC (over the counter) pills aren't usually for extended use unless under the direction of a physician.