4 month old with diarreah

My four month old has what looks like diarreah for almost a week now I took him to his Peditrician on Friday and mentioned it to her and he happened to poop when there so I even showed her and she said it was fine. He’s been sick with a cold as well. I’m going to be calling again tomorrow because I’m worried anyone else have an experience like this and anything that might help?