I also used to get those pains. They do come from the factory. However if they last long and are pulling, it could be a vericose vein on the testicle. Feels like a bag of worms under your testicle. Don't worry there is the epidedemis, which feels like a single worm, but it should not be more than that. <IMG SRC="http://www.healthboards.com/ubb/smile.gif">
The vericose vein interferes with the cooling of the testicle (factory) and reduce it size. This is not terrible, but it is better to remove it , especially if you would like children in the next 4 years.