What Causes Irregular Periods Bleeding?

Went through menapause just fine @ 45 years of age. Am now 53 and had a testosterone pellet implanted in hip every 3 months and took 200mg of prometrium first two weeks of every month. Result was increased labido and started having periods again. Did all this for about a year and stopped as the PMS was bad. All was fine for several months and now I've had a period light to very heavy for 6 weeks. Any ideas as to what could be causing this?