Could someone help me please.

Thank you for taking the time to read this.

So I had sex, unprotected in July. He didn't finish inside me but did use the pull out method (I kkow this isn't good).

My problem is now, I had a period in Aug but it was a one day period and didn't even fill one pad.

September was the same but not even a full day.

Not I haven't had one since, according to my app, I am not 3 weeks past when I should have started, I have never missed a single period since I started at 16.

Nothing in my life has changed so I have no stress, I'm just wondering if anyone knew what could cause a missed period? I highly doubt I am pregnant, nor have I checked because I just don't think it would be as had 2 cycles.

Any help would truly be appreciated, thank you🤍