I would take Yorkiluv's advice in terms of the testing - she has SO much experience with this, and great advice - PM her too if you have more questions. He could be lethargic, sleepy, not thriving - could be nauseous, drooling, constipated, excessive thirst - he might experience all or some of those w/ liver shunt, and some puppies don't show symptoms until later.
I'm so sorry you're going through this. I mean, it may NOT be this at all - but given a few of the symptoms, it may be worth ruling out. And then also, like others have said - checking the ears really thoroughly too.
In the meantime, get some canned/sliced potatoes or fresh potatoes and mash them up w/ a bit of butter and feed those every 3 hours or so. I'd stay away from proteins until you talk to the vet about testing and/or ask Yorkieluv about diet advice before testing. At least w/ carbs, you won't do harm if there is a liver issue. Hang in there - we're here for you.
