I am an airborne trooper and I am having a lot of back pain, what is wrong with me??!!?

Ok I am in the Army stationed at ft bragg nc. I had a jump a few weeks ago where I had a rough landing and hurt my back. Now it hurts to walk, run. When I drive I get shooting pains up into my lower and middle back. When I stand for too long it starts to hurt even more and I get lightheaded. The Doctors keep telling me that they cant find any reason why I am in pain. But I know that I am. Why is it still hurting so badly? I didn't break anything.