I read the other responses, and they all had good advice. I would like to pass on my experience, however, should you run into this.
My daughter was a very avid eater and had doubled her birth weight really fast. We fed every 2 hours. Well at 3 months she started arching her back while eating, latching, unlatching, crying, and being very uncomfortable. She appeared to be in pain, spit up a lot, was gassy and was very difficult to feed. She was so fussy!!
I went to the doctor after a week because I was worried she might have reflux. The doctor said that my daughter was a little piggie and was eating too much. She gave the analogy of eating a Thanksgiving meal every day, how would you feel? Boated, groggy etc.
She recommended that since she was gaining weight at a greater rate than average (1.5 ounces instead of the normal 1/2 ounce a day) that we move the feedings to every three hours.
I thought that my baby would scream at extending the feedings. The doctor said that if she appeared too hungry I could give her some tea, like chamomile to satiate her eating habit. She wont starve. Well we did it, and we slowly moved the feedings to three hours about 5-10 minute stretches over a week. Boy was it a change!! Her mood improved, she was less gassy, less spit up and I felt a little more rejuvenated.
So if you run into this behavior, you may want to extend the feeding, just a little at a time and see how he does. Congrats on your healthy chubby baby!!!