I would recommend against the DIM as it is a goitrogen-- suppresses thyroid. Iodine would be a first line therapy. If Iodine doesn't help within three months, you might try a little natural progesterone cream, 20 mg, in the last half of your cycle. The strategy is to to keep your uterine lining thin. Right now the lining is getting too big before it "falls out."
This heavy period phase should pass as you get into menopause.