Unisom is a pregnancy class A drug whereas Tylenol is a pregancy class C meaning that Unisom is safer. Additionally Tylenol comes with a black box warning since it causes acute liver failure in large doses esp when combined with alcohol.
In other words if you need it take it. I'm sure. You have employed all other strategies if you are nervous. Goood sleep hygine (no Tv or back lit devices, night lights in the room, going to bed at thesame time eetc)
You could do melatonin 1 hour prior to sleeping etc. Talk to your doctor.
If ur doc prescribed it I would double check with him/her. I don't quite understand why u would just take unisom though. My doc in the beginning had me taking 1/2 a unisom & a B6 for nausea, but only when it was absolutely necessary. When that wasn't strong enough I then was prescribed zofran.