I am pretty sure I am not preggo...

I am on birth control. For some odd reason I bled all week a few weeks ago then the week I was due for my period (I was on the white pills in my pack) I didn't bleed at all. Yesterday and today I have been feeling very nauseous. I know how it feels to be pregnant and the nausea reminds me of when I was with my son. It comes and goes like in waves. I took a test on my lunch break just to be safe. It looks negative to me but I wanted to ask opinions just to be sure.