Side pain below the rib cage.

It has been a few months since I experienced slight pain on the side below the right rib cage. It's not very painful, but sometimes when I wake up in the morning, or when I try to sleep, or during the day, I feel a dull, uncomfortable pain. Even when I don't touch it, it feels subtly sore, like when you press on a bruise. I also had an upper abdominal ultrasound, and it was said that there is no abnormality in the liver or elsewhere. Does anyone have similar symptoms or have received treatment?