Ok so about a week ago, me and my bf had sex, a few times. I had a <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> that was just "My Calendar" or something like that and it said that I was supposed to start Saturday. I got this app late last week and found out it took a lot more info on ur period. Anyway, I put in the info and this app says I start tomorrow. Now, we had unprotected sex once but he pulled out; we r sure of it. I'm just wondering if I need to be stressed about being late or just wait to see when I start. Any suggestions..?