Do you mean on and off this happens? At various times, one of your testicles will swell and be painful? Hopefully you don't mean you've had the swelling and pain for 4 years! Asking your doctor about this is important. Depending on your age, a parent should be told too to get you examined. You could have torsion which is important to diagnose. This happens if the testicle rotates and cuts off supply. You could also have inflammation called epididymitis. Very treatable. Here's a whole list. https://www.medicinenet.com/swollen_testicles/symptoms.htm Know that getting treated will probably be fairly easy and the symptom would go away so worth getting checked out!