I have had a similar problem, it was never specifically diagnosed but was thought (by a physio.) to be a minor injury, but in a place where there are lots of nerves, hence massive pain! The fact that your pain goes up your leg would support this theory. Try massaging the bottom of your foot with a tennis ball (by standing on it).
The cure for me was rest and stretching exercises for the back of my legs (the tightness of the muscles down the back of my legs was thought to be the reason for the injury). Remember whether there is a fracture or not the cure is nearly always rest! And then increase mileage slowly!
On the subject of Supraventricular tachycardia sometimes called SVT there are a number of things you can do to relieve the symptoms. You would not believe me if I explained them! Have a look at this https://en.wikipedia.org/wiki/Supraventricular_tachycardia and look at 'physical maneuvers' it (SVT) is sometimes relieved by blowing into a syringe with the plunger removed. SVT is an annoying condition that just comes and goes on its own but is thought to be triggered by some things (explained on the wikipedia site) for you it would appear to be running but I wonder if it could be running +coffee? Unfortunately the treatment takes some time, it would be nice to see an ECG while the episode is going on, but this is not easy!