Health Insurance Sucks

On fathers day I woke up with a side ache at about 6:30 am. Four hours later I could barley walk so my wife took me to the hospital. She helped me walk to the emergency room and I was admitted right away. They did the MRI of my abdominal and took a urine sample and was determined that my appendix was inflamed. By 2:00 it was the worst pain I have ever felt and I couldn't sit up or walk at all. I was in surgery at 3:00 pm and in recovery at 3:30 pm. I went home on Monday and back to work 2 days latter.
Today I received a letter from my Health Insurer saying my claim was denied. I haven't called yet but I will tomorrow and try to stay calm.
I don't know what I was supposed to do or what I did wrong? Should I have let it rupture and then go to the hospital?
Anyone ever had any luck appealing a denial? Did you have to hire an attorney?
I guess my car will be for sale if I don't win my appeal.