I don't know how much acetomeniphen Tylenol PM has in it but those without liver disease can take up to 4 gms per day -NOT WITH ALCOHOL- without risk. Those with liver disease have to cut that in half- 2 gms per day. Those with cirrhosis should take even less- I never take more than one 500 mg tab per day, that's 1/2 gm. 4 gms =4000 mg. Hope this helps.
I started out taking one, then moved up to two, now I'm on three. I've been taking three a night for about a year and a half.
It depends on how much (dosage) of Tylenol you've been taking.
Acetaminophen (at high doses) is capable of doing liver damage, even without alcohol.
Tell your doctor about it. Have a liver panel (blood test) done, just to put your mind at ease.
I had to take a sleeping pill for 8 years. I understand Tylenol PM is not as bad but any sleep aid is not wise to take for a prolonged use. It took me 6 months to be able to sleep properly without them. I was tempted many times to re-use but I am very glad I did not. I take the occasional Tylenol PM now but feel sluggish the next morning and very irritable all day. Try natural remedies to help you sleep, get plenty of exercise and do not eat a large meal before bed. Hope this helps, good luck