I thought of one more thing - search around this site for 'split dose". -- that was the major improvement for me -- maybe try splitting your dose and tapering again .
"My flare-up is really affecting my shoulders and starting into my hips. " - I assume this is how you feel in the morning ? and then you take your 5mg and feel ....any better ? many people keep a spreadsheet or journal of the Prednisone dose and and pain levels throughout the day .

also see this thread that is currently ongoing : https://connect.mayoclinic.org/discussion/anyone-tapered-down-as-directed-but-increased-back-up-on-their-own/