Hot flashes during period are worst, why?

I am nearing menopause and having hot flashes off and on. Try to use progestorone cream to ward off the flashes but I am supposed to stop using the cream when my period starts. Yet, during my period I seem to now have the worst hot flashes that I have had yet since my perimenopause started. This doesn't make sense. Does anyone know why this is happening?

Thanks, Dewyeyes