I have been dealing with the same thing for several years. It's difficult to tell where the pain starts as it wraps around my entire upper abdomen. I do have disc issues in all levels of my back. I have been tested for what seems like everything under the sun. I've had the stints put in, taken meds for EPI and restricted diet.
When my hits it's fast and hard, pain leads to profusely sweating, nausea and vomiting. I just got out of the hospital for this last attack and that Dr said it was IBS. I'm sorry you are dealing with this and I know the mental anxiety it brings with each attack. The pain is so intense it feels like you are going to die and I have begged to do just that.
My Dr at the Mayo clinic did surgery in April and found that I had a lot of adhesion of my small intestines with diverticulitis pouches the size of walnuts. I was pain free for 6 months but have started having random attacks again.
I think that Thoracic pain brings on a vagal nerve response that complicates the symptoms.
None of these issues showed up on the numerous test, Dr found out when he did the surgery for gastric bypass to replace the Nissan Fundication. I hope you get answers soon. Don't give up and advocate for yourself until you find a Dr that listens and takes your symptoms seriously.