After being diagnosed with cancer, it is easy to imagine that all illnesses and symptoms are related to that cancer. However, your PSA suggests that the RT was successful - it is expected that your PSA will rise now you have stopped the hormone treatment and your testosterone starts to kick back in. Also, advanced cancer wouldn't cause pain in all your joints.
Not good enough for your GP just to say it isn't related to the prostate cancer though - what is s/he suggesting instead? Whatever is causing your pain needs to be identified so that you can get some relief. A referral to see if you have a rheumatoid / arthritic condition would be the obvious next step.