Answer by  
                                                                                          DRS (621)
                                                            
                          
                          
                                                          There are a couple of possibilities, most of which are not serious, but you should definitely consider going to a gynecologist in order to rule out any sexually transmitted diseases.  The problem could be as simple as an allergic reaction to a new laundry detergent used to launder your underpants.  Another possibility is a bad yeast infection.