Irritation at vaginal opening followed by chunky white disch

I'm 17 and I've been sexually active with the same person for the last 8 months. I am on Yasmin birth control and often my boyfriend and I don't use condoms because we trust the pill and have both been tested. After having sex about 6 times this past weekend I experienced pain at the opening of the vagina, even during the last 2 times we had sex this weekend. The pain continued and I thought it was just from too much action but then the next day I had a pink milky colored discharge. I was worried because my periods are always regular so I stuck my finger up and when I pulled it out it was covered in a white chunky discharge that looked a lot like wet toliet paper. Much of it was white and then there were small areas that were pinky-brown. Today is the third day of symptoms and now the discharge is all brownypink.