On April 7th My Period Went Off So The Next

On April 7th my period went off so the next day I had unprotected sex. I took a plan B, but for some reason I don't think it worked.Lately I have been burping a lot and having nausea. My breast get sore but they aren't that painful. On April 12th I was spotting and up until today I'm still spotting. Another thing I did notice is I can't really finish up my food without feeling like I'll throw up and right now I have an headache.