Hi,
I think you are right about o day is when your cm starts chancing from ewcm. Bcause I have read the day bfore o is your peak day and is the best chance of gettn pregnant bcause there are sperm waitn there when the egg appears. But I hav heard that you can get pregnant on 0 day too bcause the egg can live up to 36hrs after appearing. If I was you I would be bding around 2 days bfore this cm and on that day too. I ovulated I think on 12th of January. Because my boyfriend was sick back then we only bd on that day so I don't know how much of a chance we have this month. Anyway time will soon tell

. I havn't got my hopes up to much this month bcause of that.
Hope I help you out.
Good Luck
Tracy.