How is this possible??

Let me start off with: this is our 3rd month trying for a baby.

Last month I could have sworn I was pregnant but AF showed up (or so I thought). I began using the OPKs after my period ended. And I kept getting STRONG peak lines. I read a couple things and decided maybe I should take a pregnancy test (knowing it’d be negative of course).

So my question...how is this possible?? I’m afraid to be excited because I did get my period. I am going out to buy more pregnancy tests later but has this ever happened to anyone else?