period help!

so my periods are usually really heavy the first day & only last around 3-4 days. well I started mine today (exactly when I was supposed to, it wasn't late or early) but for some reason it's lighter than normal. I've heard that stress/anxiety can change your period patters & i have been extremely stressed the past month because of starting working graveyard shifts at a new job, balancing school & a new boyfriend, & the anxiety of being pregnant (even though that chance is super low). I've already taken 2 pregnancy tests & both came out negative. so I was just wondering if all this worrying & stressing has caused my period to be lighter this month? & should I wait a day or 2 for it to become heavier??