severe constipation?

my lo just turned 4 months and i switched to Novalac Reflux from Nan Optipro gold. But now his severly constipated. to the point where around his anus is pushing out and the poo is at the end sitting there. it looks rock hard. His in so much pain 😔 anything i can do to help him past tonight? i cant get to the store until tomorrow morning. ive already tried warm bath, bicycle legs, apple juice, and water. Just want to help my little man 😣 i dont have anything else to give him.