Ladies. Please help. And respond.

Erika
Okay, I've posted a few times without really an answer. My last AF start date was December 7th. And now im 3 weeks late. I can't keep anything down. I get really light headed without anything happening. I'm feeling really sore. And tired. Craving foods I hate. I tested over s week ago and it was bfn. Should I retest? What's going on. Any advice helps. 
Ps. About a month ago I had some dark spotting. But nothing like AF. Maybe implantion bleeding??