This feels close to my heart this week as I began my first cycle taking a soy isoflavones supplement just a few weeks ago. I had had about 8 mos of very irregular cycles after coming off bcp - was tested for PCOS or other hormonal issues with negatives - but it still seemed like I wasn't ovulating regularly if at all (temped about 4 months, no opks though).
Anyway after a 67d cycle once I read more about soy and FINALLY got my period, I said what the heck? Went for it, took soy on CDs 3-7. Wouldn't you know it but yesterday CD17 got a major opk pos, and a temp spike this morning, so all signs point to OV! Sure, it could be a fluke, but I don't think it's a coincidence that my first clear OV was my first soy cycle!
My 'research' tells me, in my humble opinion, that if you have a moderately regular/consistent cycle with regular/consistent ov, than soy may not be for you. I read not only testimonials of soy ovs and soy BFPs, but stories where it threw off cycles that were already pretty regular.
I've rambled enough! Hope that helps, and good luck.
