Most likely you have jock itch!!! This is a fungal infection and quite common. you may get it from either putting on very tight underpants when your nuts are wet and the material is of a certain kind. Either that or you may have got athletes foot and when you have put on your underpants after putting on socks they may scrape and carry the infection to your mid section. JUst goto the pharmacy and ask for 'jocki itch' cream when no one else is in the pharmacy. Either that or just shout it out pretending not to be embarrased about it.