Could this be some kind of disease rather than simply a muscular injury?

It started simple enough. I woke up on May 6 and felt a sharp pain shoot down the back of my right leg. I wasn’t too concerned. I’d had hip bursitis 2x before, and the bursitis pain always disappeared within a couple of days. This pain didn’t go away. It got worse. I took Ibuprofen or Vicodan. I put ice on my right hamstring. I didn’t exercise. I rested. Whenever I woke up in the morning or moved in a certain way, I was in a great deal of pain. Finally ( on May 20) I went to see a doctor. The doctor did not even have me lie down so he could examine me. He heard that I lift weights and had likely increased the weight on the leg press too much. He said to me: ” You tore a muscle-Don’t use ice-Use a heating pad 3x a day, and don’t exercise at all. (Not even walking OMAR was allowed.) He prescribed a muscle relaxant for me to take 4x a day. I did everything he told me to do and I got worse The pain intensified and spread to my whole leg (front-back-feet-) then to both legs.