Allergic Reaction - Help

I have been on nexium for many years.  Recently, my insurance stopped covering it and I was switched to Protonix.  After taking for 3 days, I devolped an itchy rash and I stopped taking.    4 days after that I tried aciphex.  The rash is continuing after 3 days off aciphed and 7 days off protonix.  I work for a medical doctor who looked at the rash and said he thinks the rash is a drug allergy.  After calling the insurance company to get prior authorization to get put back on nexium, they denied me and told me to try a number of other drugs.  I called my pharmacist and he said that they all have. basically the same ingredients which makes no sense to me.  There must be something in these pills that is different, even the coating on the caplets perhaps?  I am in the middle of switching gastro doctors, yet am afraid not to take anything because of the severe symptoms I had prior to the nexium.  Any input on these drugs.  Thanks.