We used lactulose when our boy was severly constipated. We tried prune sachets first. Lots of water will help aswell.xx
My local pharmacist recommended a probiotic drops, to help with all my little girls tummy troubles including constipation. We still use the probiotic now (16months).
We had same situation. Bought prune pouches and cut out bananas. Made sure she has weetabix for breakfast. It worked but our girl clearly has tendency to be constipated
Give him plenty of water and then prunes or pears (can be fruit/ juice/ purée). That should help x