What Causes Sudden Pain In The Abdomen Radiating To The Chest?

I have been having sudden severe pain in my upper abdomen just beneath my diaphragm....it comes and goes, and just comes on suddenly.....it radiates up through my chest and into my back almost feels like a heart attack, it causes me to be extremely nauseous. I have been experiencing for about week and when it first started I had an episode of vomiting that came on suddenly after that the pain started....if I eat, I get a awful taste in my mouth afterwards. It kinda feels like when I had episodes with ulcers but 10 times worse and my ulcers usually didn t hurt that bad unless I consumed alcohol....and it was made better by taking omeprazole or an over the counter antacid......neither of those even phase this pain PLEASE HELP