Help!

Hey guys! So in July my period was five days late, it finally came on July 24 and only lasted about 3 and a half-4 days. That was the first time in a year that it was late like that, it usually lasts for about 5-6 days and is always on time. I went to my ob/gyn and I wasn’t pregnant Anyways...fast forward to yesterday...I finally decided to take the pill as a birth control method and before I even started it my boyfriend and I had sex(yesterday) he came in me and I just want to know what the chances of getting pregnant are and if I should wait until my next period is due to make sure I’m not to start the pill just because I don’t want to mess my body up or risk anything if I am pregnant. Glow says my ovulation is in six days. Any advice and knowledge is appreciated!