What Causes Heavy Period Every Alternate Week Along With Cramping?

I will soon turn 46 and since having my tubes tied nearly 16 years ago, my periods have been irregular (never consistant and spotting between), but just in the past year, my periods have been more frequent and now I am having one every other week. The bleeding is extremely heavy (changing tampons every 1-2 hours) and they are lasting up to five days. The cramping is getting so severe, my ibuprophen is no longer working. And recently I am getting cramping in my lower back and down my legs. What do you think is going on?