Lower left back pain. A solution,

Hi i have been experiencing this problem from past few years, however i thought it is not that serious but sometimes i feel a strong pain. i do not know whether is it a pain in the bone or a pain in the nerve around my left bum. the pain usually is strong after i masturbate or after i work out for my abs. i play sports and work out regularly and i'm physically fit. Also when i lift my left leg up and down while lying down, i can hear the crack sound in the lower back region. I also feel similar pain in my left leg near the calf muscle, i do not know whether to consult a neurologist or an orthopaedic for this issue, pain is severe after i masturbate more number of times, kindly provide a solution, thanks!!