I took plan b one step about a week ago and had mild side effect. now i started to have bad cramps like my menstrual cramps and a feeling like my flow was trying to come down. is this normal?

Plan b side effects: Not normal. Please make an appointment to see your gyn provider. Good luck.

Plan B: You generally expect to have your period within two weeks after taking plan B.

Side effects vs STI: Some women notice that their periods are off in timing +/- 2 days after taking Plan B. It is often the next month's period that is heavier or longer, not the current one. In your case, I suspect you had unprotected sex (hence the need for Plan B) and may be experiencing pain from a pelvic infection/ STI. You need to see a physician for STI testing and treatment.