I am 20, sexually active, and have very regular periods avg. of 26 days (22-28 days) my last period was on April 21st and I came down with food poisoning April 29 - May 1. I was suppose to be ovulating on May 3rd..  Some of my symptoms were as follows: Throwing up, diarrhea, low grade fever, body aches, and chills. Me and my boyfriend used condoms I'm worried because I've never been 3 days late but could it be the food poisoning affecting my period? When should I take a pregnancy test? It's been 29 days since my last period. I also took plan B the month before but my period came on time.