What could it be

So for the last 5 or 6 days I have been having excruciating pain on my lower right side. I'm to the point I'm doubled over and can't move because of the pain. I went to the er 2 days ago and they said there is nothing wrong with me. The pain keeps getting progressively worse. I don't know what it could be. Should I go back to the er or just try to tough it out