Hi, Kim,
I'm very sorry to hear about your problems. It sounds like you need some rest, and maybe Sil (sillydol) will be able to help you with some advice about walking while blisters are healing. On one of her caminos she got big blisters right at the start, and wound up walking in those well-cushioned sandals (Tevas, Keens, not sure what the brand was).
It looks to me, looking on Google maps, that you are not too far from the center, about 1.5 km from the cathedral. But right in your vicinity, there are at least 5 farmacias, which is where I would start. I'm sure the hotel desk can point you to the closest one. And if there's no infection, there's probably not going to be much that a doctor would be able to do anyway. In my experience, pharmacists in Spain provide very good basic medical advice.
It sounds to me like your boots may be too small, but buying a new pair while your feet are in this condition would not make sense, IMO.
I hope you get the attention and time to rest that you need. Sending you lots of positive cyber-vibes -- Laurie