ladies help me

Becca
Hi ladies just wanting your opinions, so AF arrived on CD 20 .. And lasted two days , witch for me is odd as I am CD 28 religiously, and lasts 4 days , 5th just mild spotting after toilet, took a clear blue and it's came back not pregnant . So thought nothing of it . But I've had constant headaches for a week now, getting dizzy spells and cramps in my lower stomach, and back pain is hurrendous! Nausea when  I'm eating and constantly tired! I don't really know what to think! Do you ladies think it was just a early AF or a late implantation?? I need your opinions😩