Important ! Please answer !

So had sex on June 6, took plan b that same day. Got my period the following week , but I’ve been feeling sick. I don’t know if it’s a stomach bug or what, but it doesn’t make sense, I got my period right after? I know plan b messes up your cycle & can give you side effects but what the... Can someone help me out ??

Also I’ve been cramping up a lot like when I’m suppose to get my period.