Not feeling well..

Sierra • Hi! My name is Sierra. & I`m a momma of a two year old girl (:
I'm a baby sitter and the kids and I are watching a movie. 
Since I've been here I've just felt awful. 
AF was supposed to visit today but hasn't yet. 
I'm feeling overly nauseous. Immensely fatigue!! 
Slight back pain. 
And VERY slight cramping and sharp random notions in my usual PMS cramping areas. 
The smells of things are making me sick and something's just don't taste right. I just want to go home and sleep! I'm kinda lightheaded and just exhausted.
I am 12DPO and tested this morning negative so I was kinda prepared for AF to come around. 
However I just started feeling all these unusual ways. 
Could it be possible I am pregnant? 
And it just hasn't shown on the tests yet?