Hard breathing, low oxegen intake, low pressure. voice become very low.x-rays, midical tests didnot show any known desease.

Low O2: Is a disease that has be diagnosed. It is hard for us to make a diagnosis here as we can't see your tests. But sob and low o2 seems like it needs more intensive work-up. The voice being low is due to the vocal cord, could be from dysfunction, allergy, etc. But i can't make that diagnosis from this basis alone. You have to talk to your doctor more and get diagnosis so you can be treated. Good luck.