I am having the same exact problem! I always used to have very heavy periods; periods so heavy that I would bleed through super tampons in a few hours. And now my periods have been so light that I hardly go four full days of bleeding and I hardly use more than two pads a day. Is there a medical reason why this is happening? I have stopped working out as much because I feared that was interfering with my period and eat the same way I normally do.
I forgot to mention that this has been happening for over three cycles, all pregnancy tests have been negative and I am experiencing cramping and abdominal pain but having hardly any bleeding, most of which is dark brown.