Your appendix is in the lower right part of your abdomen and quite often, the pain
of appendicitis will start in the middle
of your stomach (around the belly button) before "settling" more in the appendix area.
If you start running a fever, the pain increases, you're vomiting or have severe nausea, I'd definitely consider going to the local ER for evaluation.
With your past surgery, it's also possible that you've developed adhesions, which definitely can be painful.