Hi
Welcome to the forum!
Vaginal discharge with odor is caused by infection of vagina or vaginitis. This can be due to a STD or a non STD cause.
Bacterial vaginitis or vaginosis causes a white-gray discharge with fishy odor. STD like trichominiasis causes a greenish discharge with odor. Sometimes a foreign body like forgotten tampon or tissue paper is not discovered until a foul smelling discharge is emitted.
Discuss these possibilities with your gynecologist. It is difficult to comment beyond this on net without examining. Take care!