Pain and hard swollen abdomen?!

It's possible you could have peritonitis which is caused by a variety of things. One of the tests for it is to see if the muscles tense automatically by themselves (the hardness you speak of). If you have a fever or vomit, you should go to the hospital immediately. Otherwise, just watch your vital signs and see if the pain increases and/or goes away immediately for no explicable reason. If that happens, the area where your appendix area may have been reinfected and then perforated. It's rare, but it happens. I can't stress enough, though, that if you have a fever and it _is_ a perforation, it is life threatening.

Edit...

I should add that acute pancreatitis feels very much like appendicitis with similar symptoms. You might just want to shell out and get a CT scan.

My doctor