I am glad you had Burger checked for worms as that was my first thought. However, some dogs are prone to a condition called bloat which can be quite dangerous. The stomach fills with air and the intestines can twist causing a life threatening condition that requires immediate medical attention. Assuming that your boy is acting normal in every way I do not think this is life threatening or even necessarily bloat. Here is what I would try.
First, in a pup that young it is normal for the belly to get bigger after a meal...but it subsides. If you are feeding him large meals, reduce the amount given at each time and up the frequency. If you feed him twice a day, feed him the same amount in smaller portions, say divided into three times per day.
If you notice that he wolfs his food, slow him down by placing a ball too large to swallow in his food bowl which forces him to eat around it. Eating to fast can cause him to swallow lots of air which can lead to bloating.
Try not to feed him when he is excited...if he eats before he goes for a run or plays hard, that can also cause bloating. Try feeding him after morning playtime when he is calm rather than before.
Lastly, don't let him gulp his water if he is a fast drinker. Keeping water down at all times can help to prevent this as they won't feel the need to wolf it down.
If these measures do not help and he is bloated all the time, maybe mention it to the vet on your next trip....but most bloated puppy bellies do subside as they get older...
I hope this helps, please keep me posted!
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