Pregnant??!

Torie

So I had sex last Friday, using withdrawal method. I took plan B on Monday. Had abdominal surgery on Wednesday, but they pregnancy tested me and it was negative. I was suppose to by date get my period the 17 but I usually get it on the 22 every other month (came early last month) so I took a test today and it was also negative. I know plan b can throw off cycle, should I worry?