What Causes Persistent Itching & Burning Sensation In The Vagina?

hi, am geeta. 22yr old and unmarried. last time after i had sex with my fiancee i immediately took a contraceptive pill. but still i missed my periods. i did a home pregnancy test done and got a faint pink line on the strip. i have itching and burning sensation in my vagina from several months. candid-v ointment dint help. what could it be?