The short answer is this: wearing tight shorts could possibly reduce your sperm level or count but it is only temporary. The testicles are making more sperm all the time and it takes about 70 days for sperm to fully develop. The testicles need to be cooler than the rest of the body in order to make sperm, so when your testicles are held close to the body by tight clothing, sperm production slows down temporarily. The same thing happens if you spend a lot of time in hot tubs. This should go back to normal if you wear boxers and don’t spend too much time in hot tubs for a few months. If you have any other concerns about your reproductive health, it’s a good idea to talk to your health care provider.