What Causes Heavy Menstruation?

I am a 42 year old woman with one child. I have very heavy periods that come roughly every two and a half to three weeks. My Gyno recommended Mirena or uterine cauterization. I am not very comfortable with the IUD as I have read many bad things about it and heard stories from other women. Is the cauterization a viable option for me and what are the side effects, pain level and recovery time of this procedure?