First of all....calm down. Your anxiety is not helping with those palpitations. I think it is the prednisone too. The side effects from that drug are horrendous. I would take only 10 mgm tonight, but tomorrow take your entire dose in the morning. You can do that. I found out this info from my GI doctor's associate, my doctor never told me that . What is your tapering dose? My doctor always had me taper 5 mgm per week. Is this too fast for you? NEVER NEVER NEVER QUIT PREDNISONE COLD TURKEY!!! I had a girlfriend who suffered from Crohn's Disease and did that and it threw her right into Addison's.
I was on 6MP for seven years but my dose was only 50 mgm. When my doctor increased it to 100 mgm I thought I was going to die. I had horrible flu like symptoms, my pancreatic and liver enzyme levels were sky high. My doctor stopped the 6MP for a few weeks until the limits returned to normal and then placed me back on the 50 mgm. It never kept me in a long term remission.
As for the potassium...why didn't your doctor send you to the lab to have your levels checked? One more thing...I noticed you are 48 yrs old...are you by any chance going through the change? I used to have horrible heart palpitations during those years. After my periods stopped, away went the palpitations, BUT the prednisone could be contributing.