You can use this formula to see if your baby is drinking enough over 24 hours when he is on an all-milk diet.
Lower limit: 150ml x weight of baby in KG
Upper limit: 200ml x weight of baby in KG
As long as your baby is feeding between the lower and upper limit in 24 hours, you are feeding enough.
3-4 times poo is normal as long as the poo is seedy and not watery. You can refer to website below to see if it is diarrhea or not.
Diaper Decoder - Stool Types, Baby Poop, Poop Colors & Abnormal Stool - Tips & Advice - Similac
You can use other things to entertain your baby when he is awake other than carrying him. You can use a play gym or a mobile to capture his attention, or even bring him down for a stroll in the pram.