Hi Kim
First of all my heart goes out to you you must be so fed up with all this. 58 is late to be having this, but no so unusual these days. I am 55 and still having periods, and a lot of ladies are older than me on here. Sometimes if you miss months you can get a build up of the lining - hence the heavy bleeding, or it could be fibroids for example.
Were you regular until this year, and are heavy periods normal for you, or something completely new and different?
I went through quite heavy bleeding just as my periods turned from regular to skipping, but I had always suffered from heavy periods due to fibroids. Now they are very light but always massive PMT first.
I am sure you will feel happier after your appointment. You may want to ask your GP for a blood test to check for anaemia, as you could be bleeding more heavily if you are low in iron, and heavy bleeding will deplete iron stores in itself.
Hope you feel better soon