Sgirl,
I think you should tell him just what you told us. It sounds like your D has gotten worse as you taper, and that's not what you want. Not to say that you should go back to a higher dose of pred, but clearly you need to find a way to treat the illness. Personally I have had good luck with Pentasa. I'm glad you're insurance is now going to cover it (I pay $200/month and I have great insurance - lucky you to only have to pay $74!) - you should absolutely use that insurance to cover this med if that's what your doc thinks will work for you.
{{{{HUGS}}}} and I hope you feel better soon.