My DH has his appendix out in July last year and his symptoms were very much like yours...the pain started over a couple of days and he went to the doc and was told if it gets worse go to hospital - that was on the Tuesday afternoon. By the wednesday morning we were at the hospital and he was in the operating theatre by that same evening (about 8.30pm).

If you're concerned, id go straight to emergency, thats what we did with DH.