A friend of mine had to have her appendix removed a few months ago, she too had pain for a while and eventually went to the docs. In the end it turned out it was a rupture not a burt appendix so it was a slow process rather than sudden pain...IYKWIM?? She was told the pain was slowly bleeding internally pria to it bursting! She was in for three nights but she is quite delicate (read:skinny) so i think that contrbuted to her not recovering as quickly.
I would think you should go to the hospital or at least ring them and see what they say. Hopefully the letter will get you in quicker. Hope it turns out to be not too bad!!! hugs to you