What Causes Pain Under Ribs?

I had a pain for several days under rins on theright side. Its still there very mild but the pain spread to the left side under the ribs and its getting worse . i have been taking apo omeprazole from 5 days already but its doesnt help . What could be a reason of having this pain? Should i go to emergency tomorrow?On monday i have app for abdominal Usg .Is it emergency better option?