What Causes Abdominal Pain, Nausea And Diarrhea?

I ve been having abdominal pain that began about three days ago with nausea and diarrhea and has now become more of a cramping feeling. The nausea and diarrhea have gone away, and I didn t have a fever, but the pain still remains. I was diagnosed with mild acid reflux a couple of months ago, but this pain is different. This is more of a constant cramping or tightening feeling across the middle of my stomach that gets worse after I eat or drink anything. Sometimes, the pain spreads to my right side but for the most part it is in the middle of my stomach. I am concerned that this could be an ulcer, or something worse. Could this just be a sign that my acid reflux is getting worse or is it a sign of something more serious? Thank you for your help!