Joe,
I have variations of these symptoms. I have been taking prevacid a lot longer. I tapered myself off in February 2016 but I am hoping that symptoms will resolve over time. Not sure if and how long this will take but these symptoms have changed my life for the worse. I too am a 50 yo male who was always in good health and very active. Now I am the polar opposite. I have had a whole bunch of blood tests and imaging studies and they are negative or inconclusive. GP is useless. I am waiting for a endocrinolgy blood panel to see if I have some sort of "inflammatory" disease (like myositis, muscular dystrophy). Am also considering a detox program too but not sure which one. Good luck and please update us on your discussion with your GP.