What could have happened???

Okay so, Yesterday which was 3 days before my period was due, I had some spotting on my panty liner and when I wiped. When I got home, Me and my fiancé had sex since it was just spotting. Well ever since I have had absolutely zero spotting now and no bleeding, I still have some weird light cramping that I had yesterday too which I figured it’s my period starting. But can sex stop your period? I’ve heard of that happening but don’t know how true that is. The day before yesterday I took a pregnancy test and it was a very clear Negative so I hardly doubt what I had yesterday was implantation bleeding. Has this happened go anyone?