I had mine about 13 years ago. I started getting pain at the top of my left testicle about 5 or 6 years ago.
It's strange because it doesn't seem to be in one area only. Sometimes I could swear it's further up in my abdomen and others it in the testicle itself.
Not all the time mind you. Just occasionally.
I started walking nightly about 3 years ago and although I've lost weight and got a whole lot fitter it has made the problem worse.
I wear adequate underwear when walking so I saw a doctor and basically there's nothing they can do.
I don't have a hernia either.
After much frustration and a refusal to live on pain medication I ended up treating it myself with gentle manipulation in the shower.
After some time in a warm shower I GENTLY stretch both testicles downward and away from my body.
Feeling at the top of each for any changes. My right one has never hurt so I figure if the left one feels the same at the top then all should be good.
And that's it... The pain goes away. I only do the manipulation when I have pain and that's maybe once or twice a week and getting less and less.
Just a few words of warning. Be gentle. Don't over do it. If it hurts too much... Stop.
EDIT: Even if you don't have this problem you should be checking your testicles regularly... Especially at the top closest to your body.
Try and compare left and right and if you feel anything your not sure about... See you doctor.