Pain in Right Testicles

In the last five/six years, ive been experiencing severe sharp pains (in short bout) into the right testicle, enough to take your breath away, best relief for when this happens is to lay still, after the pain becomes very tender.. It only ever happen in my right testicle, it is surely very very painful... what could be the cause of this.. this happens to me 4/5 times a year.. no signs of lump, urinate well, no swelling just it become very sore and tender to touch to rub to get some relief..