lots and lots of drool, constanly chewing his fingers trying to chew mine or his daddy's, everything…

lots and lots of drool, constanly chewing his fingers trying to chew mine or his daddy's, everything goes to his mouth, biting down on the bottle, sometimes he has diarrhea, and unusually fussy for no apparent reason. i give him some baby tylenol and put a little orajel on his gums sometimes it helps sometimes it doesn't. He is almost 4 months. Could he be teething?