Please answer!

Still no AF. AF was suppose to be here the 9th. Took three pregnancy tests all BFN have been feeling weird. No cramps like AF will arrive. Tonight I noticed My areoles are like a dark purple. I've never noticed if this happened before AF comes. Is that a sign of pregnancy? I've Been feeling nauseous, headaches off and on and tired. And a lot of CM. thinking of going back to OBGYN soon if continues. Could prenatal vitamins cause this?