idiot

Boogereater isn't reading between the lines and neither are you. It sounds like OP is sending physical letters to his penpal through the mail to someone who is likely to get their mail inspected. He needs a code and decoder sheet which can stand up to scrutiny by praying eyes. He's most likely corresponding with a kid who still lives at home with strict religious parents or with someone in a religious boarding school or possibly with someone in the military or in prison in a religious country.