Why Am I Bleeding Heavily And Spitting Blood?

I have had 3 periods in the past 5 weeks. My last period which ended yesterday I noticed large blood clots when I used the bathroom. I also would bleed through my tampons every couple of hours and would have to wear 2 large pads at night to prevent myself from bleeding through. Sometimes that didnt work. Today, I was feeling light headed and very weak and I started spitting up blood