Pregnancy tests trigger periods 😂

[Funny] So my period sometimes is late because I can be a bit irregular. But I swear every single time I start to get worried and go out and buy a test, I either get my period that day or the next. My period this time was 3 weeks late. I decided to take a pregnancy test today just because it had been a while(no symptoms/ didn't think I was) and about a hour later my period starts. What kind of voodoo is this? 😂