What Causes Persistent Burning Sensation And Foul Smell In The Penis?

Hi. 25 year old male. Have been tested for STD's, and I'm clean. Have a bad history of kidney stones, doctors say my body produces too much sodium phosphate, and creates its own kidneys stones that way. have had Urine tests done as well to see if I had a UTI, and that was negative as well. For years now I have had constant burning when I urinate or ejaculate, and when my penis is erect there is also a slight burning sensation. And to top it off, there is an unpleasent smell, that wont seem to go away. I am frustrated, and hopeless. I have tried everything I can think of, and still nothing. Can't even find a doctor in my area that can lead me in the right direction of curing this issue. What should I do?