Tylenol products are safe, I have a small list of safe meds that my docs office gave me, it just says to keep the daily amount under 4000mg, which is still really high. That list doesn't say anything about melatonin though so I would definitely ask your doc
I was also told that its safe to take any Tylenol products during pregnancy to include Tylenol PM. I would rather take natural things though.
melatonin is natural my kids dr suggested it for my almost 7 yr old and 1 yr old. they both have trouble sleeping through the night. if your dr says its ok i would see an issue taking it.
I asked specifically about taking Melatonin as I've always had sleep issues. My doctor told me that its better to steer clear and to take Unisom instead because Melatonin hasn't really been tested for safety in pregnancy.