What Causes White Vaginal Discharge?

Hello, I m Alex. i have a question. I out my depo shot on August 6. when i went to the clinic on that day. One of the nurses ask me why are you late for my shot? i said the last time i was here for my 2st shot they put August 6 on the paper for my 3rd shot the nurse said they lied, your shot was July 25 . She ask me when the last time did you had sex? i told her August 1 on a Friday she told me if i had any Vaginal bleeding let her know but when August 26 hits i had a little blood (Aug. 26 - 29) after that week i had white discharge. when i have sex with my partner i see the white, thick , milky like on this penis. Me and him have unprotected sex. Is still coming out. Am I m Pregnant or no?