That's a faster than usual taper down under 10mg with larger drops than usual, with the rule of thumb being to taper by 10% of the dose at a time under 10mg. A 1.5mg drop from 7.5mg to 6mg is a 20% dose drop, so it's no wonder you had some stronger pain after doing it. And your last reduction from 6mg to 5mg is another 20% drop.

Did your rheumatologist give you a guide to your schedule of reductions under 10mg? It seems to be different in the US, but in Australia I was given a printed reduction schedule to reduce by 1mg every 4 - 8 weeks under 10mg, depending on how I handled the reduction. I reduced by .5mg every 3wks for a 1mg reduction every 6wks, which was mid-range in the reduction schedule. (After a flare at 6mg I'm now reducing using the longer range of 1mg every 8wks - .5mg every 4wks - but that's another story.)