Sky, the first thing that comes to mind is a tendon tear, especially with the falling off the gas pedal thing. Did your physical therapist diagnose it, or a doctor? Therapists are knowledgeable, but I wouldn't trust them to know everything.

I remember a few years back I was having heel pain whenever I got out of bed in the morning. Doing stairs was a killer. It got better on its own after a few weeks, so I couldn't tell you what it was.