Fishy odor smell and stain on panties what can it be is it normal?

Vaginitis: A fishy odored discharge has been associated with trichomonas infection. Other potential cause are yeast or gardenella infection. It is a good idea to have this evaluated by a gynecologist who can diagnose by looking under a microscope or doing a simple test.

Not normal; BV: Sometimes disturbances to the natural bacteria in your vagina (douching, irregular bleeding, unprotected sex, etc) can allow abnl bacteria like Gardnerella to overgrow and cause a fishy odor. It's not sexually transmitted, but can be treated w/ Metronidazole(Flagyl)/Clindamycin/Boric Acid. See your GYN for a prescription and be examined for other potential causes. Nothing urgent/dangerous though.