horrible stomach pain

So about a week ago, I woke up to horrible pain in my stomach. It seriously felt like it was on fire. The pain went away the next day. A couple of times yesterday I was having some stomach pain at work. It wasn't until I actually got into bed that the pain worsened. It was cramping so bad I was crying. The weird thing was the pain was only on my right side. Could it be something serious? Today on a scale of 1-10 I'm at a 2 with the pain. But could I have something severe? My period is due to be next week. Could it be PMS?