Christine, every time I taper down, I seem to have a bad day or two, not necessarily the same day as the next lower dose. Then it evens out. At this point, I've been on 5 mg for about a month or so, and I'm reluctant to go off it before I see what happens with the Imuran. I expect I'll probably have the same thing happen when I go off.
Hopefully this is the same thing going on with you. I don't think our bodies like change much.