What Does Pink Vaginal Discharge Indicate?

I dont use any protection when having sex with my boyfriend and im not on the

pill, i had sex three times while ovulating which was from Jan 20th - Jan 25th.

My period was due on 31st of Jan, its now Feb 6th and Friday,

Sat & today when i wiped after using the toilet, there was a tiny bit of

light pink blood/discharge on the paper. I took a "First Response" Pregnancy

test this afternoon at 3pm because the test said i could do it at anytime of the

day. It came back negative. Whats going on?