How to get my 3 month old to poop on his own? he is breastfed and strains so much without success, he has poop 3 times on his own. we have to put so much pressure on his tummy to help his efforts to poop. he strains before each feeding every 3 hours?

The straining may not be a bad thing, it may just be you over reacting to the baby's response. The baby's colonic activities increases with feeding like anybody unless the strain is bad it may be just something to observe until the abdominal muscles are stronger. The breast milk is dilute enough to produce adequate fluid mostly but you may add a little water without any harm if you want.

Infants abdominal muscles are not very strong early on, so they can appear to be straining when they are just using their muscles normally for their age. If his stools are soft then it is nothing to worry about; I would recommend not pushing on his belly and try to let him push the stool out on his own. If his stools are very hard, please discuss with his doctor.