What Causes Soreness And Pink Discharge From The Vagina?

I had foreplay with my boyfriend yesterday, and today I noticed that when I went to pee it's a light pink colour so there is blood in it. I am sore too, what should I do? I've read that I should keep my fluids up and if this hasn't gone within 48 hours I should see a doctor, but I don't want to because my parents don't know I do this with my boyfriend and I don't want to get in BIG trouble. PLEASE help!