What Causes Heavy And Irregular Vaginal Bleeding?

I am a 48 yo f who has been experiencing abnormal amount vaginal bleeding. I had my period two weeks ago and now am on my 6th day of bleeding. I soak a super tampon in about a two hour period. It s been going at this flow for about two days now. I am dizzy and light headed when I get up and I have had a bad headache for at least three days as well. I m still able to function but not my usual self. How long do I let this go?