So, my BF is in the military and was able to come home on leave for a week the ending of June. We had sex without protection. I got my period a little early in July, but have yet to get my period this month according to my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> apps. I've started working out more, but was an athlete in college so I don't think it's late due to being more active. Any thoughts as to why this could be happening?