Pain under the right rib cage.

Sometimes, I feel a dull pain under my right rib cage. It's not constant, but when it does, it lasts for a day or two, so I was worried. I went to Gut Hospital for an upper abdominal ultrasound and was told there was nothing wrong. However, the ultrasound was performed by a female doctor, so I'm not sure if she interpreted it correctly. They say the person doing the ultrasound has to be the one looking at it.

I still feel sick sometimes, but they say there's nothing wrong, so I can't do anything else. Should I go to another hospital?