My age is 31, height is 5'10", 160lbs, and I don't have any medical history that I'm aware of. My question is, I noticed that when I was younger and I would masterbate both of my testicles would get smaller and then if I didn't masterbate for a while they would after a few days or a week get bigger again. Now, the left testicle is maybe 1/2 bigger then the right one and only the right one gets smaller after masterbation and then bigger again but the left one always stays the same size. I felt for lumps and their were none. Neither one of the testicles are ever feeling painful. So my question is everything normal or should I be concerned?