What Causes Large Blood Clot Discharge During Menstruation?

I have been on my period for two days now and I have to change my tampon every half hour I have huge clots slipping past it and it hasn t slowed down im starting to feel vary tired and crampy I have almost no energy no matter what I do I leak through should I go to the hospital also most of the blood is bright red and the clots are a deep dark red or grey in color please write back asap