Uljin-gun Seoul Clinic, dissatisfaction with treatment despite symptom explanation

I felt my condition suddenly deteriorate after returning from a trip to Busan three weeks ago. Since then, I’ve had a very sore throat, an upset stomach, and a headache, so I went to the clinic (I went because I remembered you treating me well in the past...). Honestly, aside from the symptoms I described, there wasn't really a proper diagnosis based on the examination. It was a consultation that just left me with nothing but question marks in my head. I took the medicine they prescribed, but it didn't really work, and I had diarrhea for three days. I don't have any drug allergies, so it seems something just didn't agree with my stomach. In the end, I stopped taking the medicine, took an anti-diarrheal, and stopped.
I still have similar symptoms (stomach upset, sore throat, and headache) that haven't gone away, so I think I need to go to a different hospital.