I been having pain in my scrotum and the veins are swollen and my right testicle is way smaller than the left one and it hurts all the time.?

Varicocele: Swollen veins inside the scrotum can be caused by a varicocele or varicose veins which can slow down the testicle circulation and thus produce pain because of lack of oxygen. Having the varicocele on the right side for a prolonged length of time not only causes atrophy or shrinkage of the testicle but also causes decreased sperm production.