Fungus or eczema
Burning is a hallmark symptom of athlete's foot
pedis), which can cause "knots" and blisters; but there is a type of eczema
called dyshidrosis that can do the same thing.
You could also be allergic to some component of your shoes, and there are other possibilities. You really need to see a dermatologist and sort this out - 3 years is long enough to tolerate burning blistering feet.