Concered woman, welcome... It's really hard to say what the problem might be. Since your Dr. is the only one with your medical history, I'd ask him/her.
Do you have osteoporosis? If so, you usually don't feel pain until you've sustained a fracture, so if you haven't injured yourself lately, then I don't know what this could be. Also, if you are taking any medications, they could have side effects of this nature. But you don't mention any meds.
Best thing is to see your Dr. and find out what's going on. Since this is affecting your walking then I believe this is very important to find out as soon as you can. If for some reason you don't have insurance post again with more information, so we might be able to suggest places you could be seen without insurance.
Good luck and let us know what you find out.