How long does nausea last after taking plan b?

Early this month I flew down to FL to see my fiancé. I was only there for 4 days, but everyday I was there we had unprotected sex. I arrived on a Friday, and that night we had unprotected sex and he ejaculated inside of me. Within the next few hours I took plan be. The next day, the same thing happened, and I took plan be again. After that occurrence, he pulled out every time for the 2 days we had left.

This all happened approximately 3 weeks ago, and i'm very nauseous. After taking the pill, inwasnt nauseous at all, but i started feelin sick last week or so. It comes and goes but I seem to get a little more sick in the afternoon. I've been having cramps but they don't feel like normal menstral cramps. My breasts are also very tender and I've been more tired than usual.

I am set to have my period this week, and I already took one home pregnancy test, but I was told that since I havnt officially missed my period yet, it has a greater chance of showin negative (which it did) and could be a false reading.

Do you think I'm still nauseous because I'm pregnant or is it just a long term side effect of plan b?