Why do my testicles hurt?

I feel uncomfortable asking this, but it needs to be asked. I recently moved and during the moving process my body was getting really hot. After I started to relax my testicles started to hurt. The pain went away for about 5 days, and then it came back! Now it just comes back at night when I start to relax. Why is it doing this? My family is known to have testicular cancer, but I have felt and found no bump/lump and no problems. It just for some reason hurts. Can someone please give me a mature answer? Thank you.