My guy has had quite a few on and off days the last couple of weeks. He is a week away from 4 months old. He is normally a VERY happy, smiling, good sleeper. The last couple of weeks he had a few REALLY off days. He was grabbing at his head really bad and very sleepless evenings. He was really restless during the day as well sometimes. He very suddenly found his hands and has been going to town on them. I don't really see much in the way of teeth emerging and the drooling isn't too excessive, but I know they can have teething symptoms well before the teeth cut through.
The interesting thing is that his breastfeeding frequency is the same. Lots of make up nursing in the evenings on the weekdays I work part-time and lots and lots of nursing on the weekends.