Welcome to health care magic.
1.The possible cause in your case seems like recurrent inflammation.
2.In this case you need to get an
ultrasound scan - it is investigation of choice.
3.The ultrasound scan will help assess the testicular parenchyma, vascularity,chord, epididymus and vessels conditions.
4.As you asked
varicocele - yes it can be one of the cause - also ultrasound will help to confirm.
5.Its good for you to avoid the conditions which causing sensitivity.
6.See your GP and get the needful investigations and treated accordingly.
Good luck.
Hope i have answered your query,
any thing to ask do not hesitate to ask.
http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888