When to test

My periods usually start at 23-28 and lasts for a week. Well I've taken Plan B about thrice this half year and messed up my cycle but still there. We did it on 6/16 and 21 and I'm about 5 days late my period. This is my first test ever in life and I'm very much confused. It says to do it BEFORE, ON, or one day AFTER expected period. But I'm wayyy past that. I took one today but my second urine of the day and it was negative. Help?? Anyone?? When's the next day I should test??? 🤔🤔