HELP PLEASE!!!

Tasha

i have been ttc since september...my periods are always on time with a 28 day cycle. this month my period has come 1 week early...its more brown discharge than blood but been going on for 4 days now and doesnt seem to be stopping anytime soon...anyone else had this happen? so confused as my period has never been early before! i have 2 children already and had 2 other pregnancies and this has never happened before :-(