I am suffering severe rectal pain during my period, what could be wrong?

Endometriosis?: If only during periods, this may represent rectal involvement with endometriosis. Often not the cause, so a thorough rectal exam to rule out other causes like hemorrhoids, anal fissures or just simple constipation ( common with menses!) is strongly encouraged, so see your doc!

Maybe constipation: Rectal pain during your period is unusual. Many people do get constipated during their period, which could cause pain. You should discuss this with your doctor.