Missed period

I have followed my cycle to the key since downloading this app 3 months ago. I am now on day 2 of a missed period according to this app. I am on essure... Which is a perminate birth control that I got back in jan of 2014 and I recently (last week) was just put on zoloft for my depression/ anxiety. I really hope it's not pregnancy. I just haven't even felt any pms or anything like I usually do. It's weird.