I Am On Birth Control And I Do Take It

I am on birth control and I do take it everyday at the same time. My period started last wednesday on time, but it was very light and it lasted for 2 days, and then came back for another day or two; still very light to where I could use a liner and be okay. On Saturday night I took a pregnancy test and it was negative... today is Tuesday and I have slight white/creamy discharge that came out one time. I'm not really sure what's going on, I'm also not trying to get pregnant.