Suggest Treatment For Possible Stress Fracture In Ankles

I believe I may have a stress fracture in my ankle. The first doctor I visited, during my routine sports physical, said she believes that I may have a navicular stress fracture in my right ankle and that I should see a doctor to get it checked out. I went to a different doctor the same night and he said that he believes it is just tendonitis and to rest it for ten days and if it doesnt get better, than it may be a stress fracture. Nothing showed up on x-rays, like we figured it wouldnt, and now I know the only way to be sure of the stress fracture is to have an MRI. I rested it the ten days, and during normal activity, it still hurts! My question to you is, if I see another doctor, would they treat my injury as a navicular stress fracture without knowing if it certainly is just that? Would they cast me for 6-8 weeks without knowing for sure? There is no way I can pay for an MRI, and dont see the problem in treating it as a fracture and resting it with a cast for the 6-8 for it to heal, stress fracture or not.