What is Regular? Post chemo menstrual cycle.

scputman

I had a Grade 3 Stage 2 lump removed in August 2011 just before my 31st birthday. I completed FEC-D in Dec 2011 and 37 RAD treatments.During this time I had no cycle.  My cycle returned in September 2012,  it has been pretty consistent about every 17 days although it seems pretty light and it is short. I am not sure of what normal for me would be, as prior to my Cancer I had been on Minera and previous to that on birth control since age 16( with exception of my two pregnancies). This month however I missed my cycle. I have taken preganacy tests and have had blood work to confirm I am not pregnant. I had a PAP and a Transvag Ultrasound in Febuary as part of my Ovarian screen all were clear. Waiting for hormone level tests to come back. Has anyone missed cycles after being regular for 8 months?