Weirdly early

Samantha
According to <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> (witch is usually pretty on point) I was sopossed to start my period on the 19th but I started yesterday. I have no idea why. What kind of things will screw with your cycle like this? Is this okay? Am I okay?