Missed

My boyfriend and I last had sex at the end of May. It was in the middle of my period week (after the first few nights I tend to be very light at nighttime) and we used protection. We haven't had sex since then due to our long distance relationship. I had a period at the end of June that seemed pretty normal for me (4-6 days of normal flow). I expected my period again towards the end of July but now it's August 10th and I still haven't gotten it. I had some brownish discharge (sorry to get graphic) yesterday so I thought I was getting it since that sometimes happens right before, but still nothing. We've never had unprotected sex and while I know it's still possible to get pregnant, I'm fairly certain I'm not.