Could it have been food poisoning with syptoms dragging on or are they pregnancy symptoms?

I had my period about two weeks ago. I havent had intercourse after I got my period though. I'm at low estrin fe BC. I have been feeling nausea and dizziness. I woke up the other morning at 2 a.m. to vomit. Have not vomitted since then though! However I have felt faint nausea feeling through the days.  Could it have been food poisoning with syptoms dragging on or are they pregnancy symptoms? Oh, and I took a pg test at 2 a.m. when I was vomiting and it said negative! Any help?!