It's not unusual that a hatchling BP is active relatively quickly after feeding. They have a much faster metabolism than their elders so it's recommended to feed them more often than you would feed an adult. If you aren't already, I'd try feeding him twice a week with an appropriately sized meal (every 3-4 days).

A hopper mouse is the size that a hatchling BP right out of the egg would generally take. Having said that, you're doing the right thing by using the fattest part of his body as your guide (if you have a scale, you can also use the feeding guideline of 10-15% of his body weight until he reaches 500 grams or so). Of course, as he grows he's going to need larger and larger food. My suggestion is to try him on a fuzzy rat next time around and see how he does. Rats, obviously, get bigger than mice and it'll be more convenient for you down the road to feed a single rat versus multiple mice in one sitting. Once he's big enough for small rats, then you can usually back down to once a week feedings. And, if you're sure he's a male, small rats will be all the bigger he'll likely ever need.

If you haven't seen this chart already, here's a reference for you that compares the sizes of mice versus rats that way if you do decide to switch it up:


Good luck with him! Consider yourself lucky to have a great little eater on your hands.