What are you feeding
There are many foods that are "constipating" to a young baby being introduced to solids, things like bananas, raw apples, carrots and rice.
Try to figure out if this is the case and modify your infants diet
. Any fruit that starts with a "p" help you "go" , peaches, plums, pears, papaya etc.
Always consult your doc so you both can determine the best course to take.