Original post by pixiepeepDon't know if you've seen a Dr for this yet, but definitely do.
Also, not a Dr, or med student etc, but I've had gallstones, so maybe I can impart some knowledge:
Gallstones typically cause sudden pain, that may start off as bearable, but increasingly gets worse, or just starts and hurts a lot, but the most common pain comes in waves, like a spasm. They usually last between half an hour and 5 hours. The pain is described as worse than childbirth. I deal with pain pretty well, but the worst attacks almost completely took my breath away, couldn't get into a comfortable position at all; most hurt that much that I actually couldn't even cry. Agony, in other words. A 10 on the pain scale.
12-15 hours sounds like a really long time - I had gallstones, my longest attack lasted about 8 hours, which was the one they ended up removing my gallbladder after! But by that point I had a huge infection and other problems... hence why I suggest getting yourself checked out - I waited too long.
It may not be actual gallstones, could be bile duct related, or gallbladder disease.
But seriously, go get it checked out. A blood test will show up liver enzymes if there's a problem near your liver/gallbladder, and an ultrasound will show any stones if they're there.
Hope you feel better soon!
EDIT: sorry, meant to add, the pain I had was about half way up my rib cage in my back, and the worst of the pains made me feel like someone had stabbed me straight through from my back through to my front. It can go up into your shoulder blade, or down towards your legs - if it heads for your legs call an ambulance - well, that's what they told me at the hospital anyway.