Confused???

Lakin • Vi Veri Veniversum Vivus Vici
So ive heard having sex can delay your period is that true? I'm suposed to start today or tomorrow. I'm one the 3rd placebo pill of my birth control but my calendar on <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> shows I shouldn't start till next week.