Barb I am actually alergic to poison ivy so I am crying for you. I had a case so bad last year that I had to go on meds for the itching - worst I have ever had.
One thing that helps me is to "wash" with Technu by Tec Labs. A EMT told me about this stuff and it works. It actually "grabs" the oil that is causing the rash, and makes it so it will wash off the skin (and clothing/fabric and pets) when rinsed off with water.
Not the total cure but it really helps to stop the "cross contamination" as the blisters form and break.
Keep checking in with your doctor too.