Mine starts out like yours real dark brown discharge and the the next day I have a really heavy flow ,then it is light, next day spotting and it is over. I have asked the dr and he said that it is normal.I asked because mine only last 2-3 days and it worried me.But I dont get away so lucky I have sever cramps

with mine.But just so you will know and your dr will know I would say something about it.