Hi Lizbeth, I don't have Addison's, but like you I also went through testing for it. I had the ACTH stimulation test - I'm not sure if that's similar to the blood test you mentioned having. My GI decided to test me for Addison's, because he said that sometimes Addison's can mimic Crohn's-like symptoms (diarrhea, nausea, weight loss, etc) and it also responds really well to pred. Apparently the ideal dose of pred for an Addison's patient is 7.5 mg per day, and I had a really good response to a trial run of 10 mg/day, which is why my GI suspected Addison's. It was ruled out for me though - I hope it's ruled out for you as well.
Do you respond really well to a low dose of pred? Do you have any skin discoloration/darkening? I know that's a common sign of primary Addison's (secondary Addison's doesn't cause skin darkening). Hopefully you don't have Addison's - I know it's quite rare, about 1 in 100,000 people have it from what I've read. Most doctors don't know much of anything about it, so that's promising that your doctor is testing you for it - best case scenario, you can rule it out and not worry about it anymore. Good luck with the bloodwork, I hope the results come back quickly and are normal.
But if you do have Addison's, you should still be able to do okay. A low dose of pred usually keeps it in check quite well from my understanding - and I think 7.5 mg is low enough that you wouldn't get moon face or many side effects. Anyway, please keep me posted on the bloodwork results, and best of luck - I hope it's not Addison's!