My little one hasn't gone potty for three days now. The doctor prescribed…

My little one hasn't gone potty for three days now. The doctor prescribed Ukrliv (for dissolving gallstones in general) and Smecta. I don't understand why everywhere it says that Smecta is used for diarrhea, but I think because of this powder he's not going potty anymore. I don't know what to do now, should we wait? We're only breastfeeding. He gas well and has a soft tummy though.