Plan b question

Jillian

I took plan b 42 days ago, I’m 11 days late on my period and I’m normally very regular, I’ve taken 3 pregnancy tests all a week apart and they’ve all said negative. I haven’t been eating much I just haven’t been hungry my cravings are all the same tho, and I’ve had back pain. Is this normal with taking plan b?? Should my period start soon?