what can cause an inflammation of a tube behind left testicle?

 hey there usually pain and swelling behind the Soft part of the testicle is known as epididymitis and is Usually caused by an infection. How old are you? Are you sexually active at all did this pain Happ and all the sudden or kind of slowly get worse? How bad is the pain on a scale of 0 to 10 zero is no pain and 10 is the worst pain you’ve ever had in your life?