Mine seemed to hit exactly all the indicators for a stress fracture. #1, it came on quite suddenly, toward the end of an otherwise normal training run. I started hurting about 1 mile before the end and barely made it home before the pain became too severe to put weight on the foot. #2, it was very painful when flexing the forefoot under any load, but much less when held rigid, even with weight on it. #3, the pain was very, very localized--pressing my finger on a particular spot on the third metatarsal just about sent me through the roof, but I could press all around that spot with basically no pain.
Stress fracture or tendonitis, anything that hurts that much requires time off from running. I agree, though, that tendonitis it shouldn't require 10 weeks.
What you have sounds to me more likely to be tendonitis. But I'm no expert. Read as much as you can about the symptoms of each. Or see a doctor, but that won't necessarily help if the person you see is as incompetent as the one I was sent to.