Help me plz..i am having a sever pain in testicals......?

i m male 25 year old.......... dont know how to tell this but i have to.....guys whenever i m turned on or do a little dry foreplay with my girl friend, my testicals( balls ) start hurting severly !...i tried mastrubate after ...but pain still exists for couple of hours.!!!!! i am still virgin .so what would be the problem n any solution ?please its serious....i want u r advise before i visit a Doctor..........