A watery, yellowish or greenish bubbly discharge with unpleasant odor, accompanied with pain and itching when urinating can be a sign of trichomoniasis, a vaginal infection with organism called Trichomonas vaginalis.
It is a type of STD usually caught by unprotected sexual intercourse.
Oral antibiotics are treatment of choice.
Even if the T.vaginalis isn't a cause, your symptoms can be explained only as STD symptoms, so, you'll need to get tested.