Nightmares?

So Alexis has been waking up just screaming and shaking and won't let me put her back down.  She hangs on to my shirt for dear life and claws until I hold her tight.  I know she's teething again, could it be the pain? Or nightmares? I give her Tylenol and then when I do get her to sleep, I put her back in her crib.  When she wakes up in the morning it's nice because she wakes up happy, but its the middle of the night that this happens.  It's breaking my heart and making me very much sleep deprived along with everyone in our house!