Implantation?!

So, husband and I have been TTC for about a year. I have PCOS and metformin didn't seem to be helping so in July doctor put me on keto diet to go with metformin. Since then I've lost 25lbs and have had two regular periods and ovulated both times successfully (had no ovulation prior). So ovulation date was 10/6... Used preseed... Today I am spotting ever so slightly.... Just a little reddish pink mixed into CM. Way too early for AF spotting, is there any other cause for this?! Trying not to get too excited...