Hi, I took Plan B on April 20th. My period started that day and lasted a full 7 days. I had sex again on April 26th, but I m positive he wore a condom. However, I m not on birth control. It s May 24th and I haven t had my period yet. Can my cycle be thrown off because of Plan B? My cycle is typically irregular as it is, so I wasn t sure if this was normal and I m paranoid or if it was Plan B or if I need to take a test?