15 days late and progesterone pill ??

This weird thing was going on that caused my period to last for over three weeks. I took Primolut N until the 6th September then the bleeding finally stopped. I had unprotected sex on the 8th September and my period according to my app is 15 days late.

I took a pregnancy test last week which turned out negative. I plan on taking another just to be safe.

Does anyone think however that maybe because I bled a bit at the beginning of September I did not need to get a full period in tht month ?

Or possibly could Primolut N have changed my cycle to how it initially was ?

I’m 16. Please help.