Kidney stone. Too many x ray on my body?

I'm a mariner. Recently while undergoing company medical check up before joining vessel, I was diagnosed with kidney stone. Right kidney, mid pole 4.1mm and lower 3.2mm. Left kidney some concretions. I don't have, any symptom nor have I ever had any considering I'm very adventurous and athletic person. I nor anyone in my family had kidney stone ever. Local urologist gave potrate and aquazide which I took for a month. Now usg shows left absolutely normal but no change in right kidney. I cannot be at home for so long. Hence have decided to go for Lithotripsy. But in x ray stone I not visible at all. But there is some gas visible in x ray and doctor says to take dulcolax and go for x ray again so that gas is cleared off and we may see the stone behind it. After taking dulcolax, I have taken x ray empty stomach.  Still x ray shows the same gas part and no stone is visible. What should I do to get a proper x ray? What are the harms if I take too many x ray on my body? It's been 3 in 1 month