I Have A Mass On My Pancreas That Was Found

I have a mass on my pancreas that was found in Dec by endoscopy. The mass had grown 10 times since June. I went into hospital, and they were unable to find the mass using MRI & CT scanning. I'm in a lot of pain, sweat a lot, am nauseated. .. is this common to miss? It's now almost May, and I don't know if it's grown even more. My GI Dr doesn't take my insurance anymore, as of Jan 1st. Any suggestions? Should I go to the ER?