Personal experience:  this sounds a lot like me.  I took an herb called Vitex
Agnus Castus, which is reputed to balance female hormones, 1-500mg capsule
twice a day with a meal, for the last half of my cycle.  It helped a lot (or
the placebo effect was very strong!).  My flow decreased by 60% in my
estimation.

I would have taken birth control pills, but they screw me up in other ways
(blood pressure, weight gain, depression), so I couldn't use them.
J. Rachael Hamlet
Author, The Breastfeeding Advocacy Page
http://www.clark.net/pub/activist/bfpage/bfpage.html