Can plan B mess up your cycle for more than 1 month??? I had sex on Jan 11th, and took it within the hour afterwards, and then started my period Jan 15th and had a full normal period, it was a few days early but other than that completely normal. And now I was supposed to start yesterday (I know I’m not really late but I’m usually like clockwork) and I haven’t. So could it be the plan b still messes with my cycle, or am I just stressing myself out? I haven’t had sex since that day either.