someone help!

sooo...I'm 16. My current boyfriend & I have been dating for 6 months now (absolute achievement nowadays) & he's the one I lost my virginity too. I haven't had my period since July. We had sex on August 18, I know very precise, the day I was supposed to start my period according to <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>. He came in me. I haven't had my period all month. Today he cummed in me again. How soon will I be able to tell if I'm pregnant?