Hi and welcome to HCM.
This can be caused by infection and you ll see will it improve on antibiotic therapy. But sometimes testicles shrink in healthy people and this is caused by cremaster muscle. This is especially expressed in cold
wheather and water so try to avoid it. Nothing serious can happen to your sperm count
or ferility, it can only be unpleasant. There is no specific cure. You can wear warmer underwear.
ALso if ther is oenis shrinkage too you can take certain medicines,Asko your urologist
WIsh you good health.