Thanks for all the suggestions, guys. The doctor did mention Morton's neuroma, but when I told him the pain was not in one precise place he said that's probably not it, then.
I have been keeping off it almost entirely. I'm just going nuts sitting around on my ass doing nothing, and not even being sure if it's helping or not. Most of the time it feels fine, but then if I try to walk or stand for a while, the pain comes back. But I really feel like I need some exercise. I've been doing some situps and such, but it's not the same as going out for a long walk, which is something I'm really used to doing.
I only have two pairs of shoes. They are both minimal shoes. Any other type of shoes cause pain in my knees and back. I have certainly found that it feels better if I walk on softer surfaces (grass, carpet, etc.), but I don't think I can do insoles. My shoes hug my feet rather than "supporting" them (feet do not need support, particularly arches - what happens if you shove a support column up in the middle of a Roman archway? - it weakens the whole structure, and the same thing happens to your feet). I've been fine with these shoes for years. I never had a problem until I tried jogging, which is what makes me think it must be the bone. But the doctor didn't find any fractures. BUT he also said there could be a fracture that would only show up on an MRI, so I might still have one. BUT he said fractures always heal within about 6 weeks, so if I had one, it should be better by now.
Insoles wouldn't fit in my shoes, and I truly cannot handle any other types of shoes. I tried putting on a pair of old shoes once, about a year and a half ago, and it felt like I had rocks strapped to my feet. It hurt terribly. I didn't even last an hour. I did just buy a new cheap pair of flip-flops which are soft without any "support" or structure, but the weather has cooled off again so I can't really wear them. The good news is, once I get back to Prague (2.5 weeks!), the weather will be much nicer there and I can wear sandals or just go barefoot. And it's much easier to stay on grass and such there. I have a pair of nicely cushioned sandals at home in Prague which I can wear for a while if hard surfaces are hurting me. And once I'm there, I can go to a proper doctor and get all the tests I need without it costing me anything.