What Is The Reason For Having Periods Even After The Flashes Is Stopped?

At age 44 diagnosed with breast cancer. I was nowhere near perimenopausal. Did six sessions of chemo - 3FEC + 3T. Period stopped after first infusion of T which was Aug 2009. Severe hot flashes night sweats and amnorrhea for 10 months. All of a sudden hot flashes /night sweats stopped and I started menstruating again (however much lighter than before treatment). Period resumed June 2010 until May 2011. I started getting flashes and night sweats again for about a month, then that stopped, however my period has not returned. Missed June, July, and now we are in August. If the flashes stopped why did I not resume my period? Am I now post menopausal or can I expect my menstruation to start up again. Thanks, Roxy