4 Days isn't a super long time, so don't stress too much. Do you know the last time he pooped? I know my Pacman is reluctant to eat when she's brewing up something special for me.You can feel their poop on the right side of their body when it's getting closer to the "exit", sometimes you can even see it as a lump, lol.
It may also be helpful if you could answer some of the information requested here. It may help narrow down why he isn't eating if the bath doesn't work.
I assume you want to give him a bath to help him go? If so, you just need to find a container he can safely sit in with warm conditioned water (some prefer to do exact temperatures, I just feel the water to make sure it's warm enough and not too hot) that goes no higher than his chin. This can be pretty effective on its own, but you can also add some honey to encourage a poop. I usually do about 15-20 minutes and cover the container with a washcloth so my girl feels safer. Sometimes they poop during the bath, sometimes after...sometimes it takes a few rounds to work. Once took my frog three days, one bath a day, to help her go.