Pregnant?

Missed my September period... But late September I had unprotected sex (with my fiance) and took the generic brand of plan b called next choice. I have taken this before (worked great) with no side effects at all. Before I took next choice I had taken 2 pregnancy test that were both negative. But today I've been very nauseous and throwing up and my breast are tender. I took plan b on September 28th. After unprotected sex on the 27th