I started weening my first at a year old, I got pregnant the next month, so I was obviously ovulating...but did not start getting my period again until two months after I completely stopped breast feeding my second. I went from September of 2004 to August of 2008 without having one period.
I am also sensitive to hormones. My milk supply started drying up upon trying the mini pill after my second. I have tried 4 different pills and have always had uncomfortable cramping and such, so my husband got a vasectomy as our form of birth control.