My diarrhea won't stop.

My son started to have a mild stomach ache since last week, and then he began to have diarrhea. So we went to the internal medicine clinic and got some medication. It definitely included an antidiarrheal. However, the next night he even developed a fever. He's still having diarrhea despite not eating anything. We thought maybe he caught a cold because he has been eating a lot of cold foods and summer treats, and sleeping with the air conditioner on, but since the medication hasn't helped, I'm worried it might be something serious and feeling anxious. Should we consider moving to a different hospital? This is a big problem...ㅜㅜ