How do I get my son to stop this sinful nonsense!?

I am a protective parent because I live in a world that does NOT have my family's best interest in mind most of the time. That is a fact we all must face. As such, I try to raise my children and husband to be FAITHFUL to the LORD GOD and respect MOTHER NATURE! I am sure many of you can agree with those same ideals. When I do the laundry I check to see if my son has been having wet dreams in his underpants. I only do this because it is the ONLY way I can get a straight answer about his masturbation, which is something I DO NOT believe is a good idea for teens to be doing. I think it is best to wait until marriage until doing ANYTHING sexual to your body. It just is the way LORD GOD intended. Lately I have been curious as to how he could be having SO MANY wet dreams in his underpants. Typically my sons have had them about once a week, not every night! He is aware of my checking seeing as I make no false attempts to hide my intentions and I worship no false idols. I think he has been trying to throw me off his track by masturbating into his underwear instead of into the carpet or kleenex. Not only has the frequency of his 'tracks' been rather high, it has also been in an odd place once or twice. I'm not a man or boy so I don't know what its like to have a weenis but I know perfectly well a semen track in the REAR END of a pair of male underwear does not happen by chance. I am very upset that not only has my son been disobeying my wishes but he has been openly deceiving me and has likely been relishing in the fact that his mother is touching his ejaculate. Why else would he continue this? My other sons obeyed because they knew how shameful it was to make their own flesh-and-blood mother touch their ejaculation streaks. I need a CHRISTIAN way to handle this situation. I will not lay a hand on my son, so DO NOT suggest anything of the sort. I love him and only want what is best for him. I DO NOT want him living a sinful life of sexual decadence where he freely releases his seed all over the house HIS FAMILY shares! Please, for those of you who have been through this (on either his end or mine), what do I do!? Thank you and GOD BLESS YOU AND AMERICA!