Why does it feel like my guts itch?

I started taking Tylenol pm a while ago cuz I couldn't sleep. It was expired but I took it anyway. And it was also extra strength but I took 4 instead of 2 because 2 wouldn't put me to sleep. Anyway, the first time i took it I would get this extreme itching type of feeling inside me like my stomach or whatever but that was only if I woke up. Now I get that feeling at random times and sometimes it lasts all day. I haven't taken any pills in at least 2 weeks though. It's like this itching/tickling feeling in my stomach, guts, intestines, inside my rib cage...whatever. It's so weird and hard to explain. It used to go away if I ate but now it doesn't. What's wrong with me?