so I've never really had a regular period and I've had mine for about a year (I'm older than thirteen so) ANYWAY <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period apps</a> never get my period right and I can't find a pattern on any calendar myself. I have, however, always been underweight, I'm in the 21st percentile with my weight, height and age. I exercise a fair amount and eat good unintentionally... is there anything that you think could be causing my irregularity?