I feel a tearing sensation in my calves or thighs, quite randomly as far as I can tell. If I ease off it sometimes fades.
This is anecdotal, but it sounds more like you’ve damaged your leg muscles, and not been able to give them a period of time, entirely devoid of riding, long enough for them to recover.
A mate suffered for years with a microtear in his calf muscle, purely becuase he would never stay off the bike for long enough for it to recover completely. I managed to give myself something similar training for the etape last year. An evenings hard road racing during my build up long distance training ripped my right calf. Took a few weeks off the bike completely as I didn’t want to nadger up 12 months of training for the etape. I escaped.
I have no idea if CK would be raised in those circumstances. Your GP is suggesting 10 days off the bike, complete rest before another test. Could be the best thing for you. To get proper advice you may need to see a proper sports physio, not a masseuse, as massage alone won’t resolve the problem.