I took Plan B, 24 hours after I had unprotected sex. My period came a few days later than normal, but started with light pinkish brown spots and then turned to red. It was much heavier and lasted 3 days longer than normal ending again with the light pinkish brown spotting. I also had much more cramping than I normally do with my period. Is it possible that I had a chemical pregnancy?

A chemical pregnancy is another term for an early miscarriage – one that is detectable by hormonal tests but not detectable by ultrasound. Being that you took Plan B within the recommended time to prevent pregnancy, it is certainly possible that you had a miscarriage as a result of the Plan B. Furthermore, your symptoms appear to be consistent with increased uterine shedding often observed during miscarriages.