Plan B Nausea and fatigue a week later?

I took Plan B on the 15th and started feeling nauseous, very fatigued, getting dizzy and having horrible insomnia a week later. I am supposed to start my period today and usually do at night, but I did not last night. That alone doesn’t concern me, but the symptoms combined with having NO pms is concerning me. I took Walgreens pregnancy tests and god a VERY very faint positive on 4 of them, but saw that Walgreens notoriously give false positives. Has anyone ever gotten these symptoms so long after taking plan b?