Could be a number things. Try drinking a bottle or two water, could be your fluids are low and it's causing cramps. It could be gas and/or constipation, in which case the only thing for relief is to work the gas out by moving or having a bm. It could be false or early labor. If you've seriously been in pain for 8 hours and it's so severe you can't move than its probably time to go to the ER and get checked out.
I'd think early labor first, appendicitis second. If you haven't yet, call your doctor's night line for advice, or go to the ER.