4 month constipated! HELP

Karissa

my son is 4 months old and he's formula fed. since the 10 of September when Irma hit Florida he's been constipated really bad. its now October 4th and still constipated. on the 25th of September for his 4 month check up I told the pediatrician about it to see if he could possibly perscribe him anything and he said no that just start him on solids meaning fuits and vegetables stage 1 that, that should give him a boost to have a bowl movement and still he hasn't . I try at least 1 time a day with him seeing him in pain helping him push out hard huge green clay type of poop hurting and widening his anus . doctor also said give him 2 oz of apple juice or prune juice with another 2 oz of water and still nothing has worked!!!! idk what else to do cause he's in so much pain . he's holding it all in . any other advice ?