Deperate mom here...

Hello parents! My 12 months old baby is having a hard time pooping, He haven’t poop for 4days . Today he’s trying, but he’s in pain. He doesn’t want to eat , finish or drink his milk . I offered him lots of fluid, massage his body, and warm bath, but it seems not working. I called his doctor and they’re seeing him tomorrow. They just pretty much said to give him lots of water and fiber for now, which is i’m already been doing. What is going on? I’m paranoid. What did you parents do when this happens?