What Causes Brown Vaginal Discharge And Cramps After Unprotected Sex?

Hi, I've been taking microgynon 30 for around 5/6 years now I have missed one out of this months packet and also had unprotected sex then took my pill after which I was late in taking, I have noticed a brown discharge when I wipe going to the toilet, also having a dull ache almost like period pains am I pregnant?