18 month baby constant constipation, very hard stools and cries when pooping. The only relief is glycerin. Tried prune juice and veggies nothing works?

Call Pediatrician. Likely just extracts too much water from stool, leading to constipation. Can try apple juice as often better tolerated than prune juice (in quantity needed to help). Ask pediatrician about daily use of MiraLAX (polyethylene glycol) (1/4-1/2 cap in bottle of juice) to help keep stools softer from "above" so glycerin needed less often "below.".