If YOU notice a difference in how you smell, and you really should know, get yourself to your gynocologist right away, it could be any number of infections.
BActerial Infections from WebMD
I can't find the actual link, but there are many different things that can cause a change in odor, where you are in your menstrual cycle, pregnancy, infection (if you are itchy it could be either Vaginitis or Bacterial Vaginitis), change in diet, change in stress level, change in hormone level (Have you switched methods of birth control?) even aging.
Or your boyfriend could just be really tactless.
But I'd stil go immediately to the doctor.