Once you're a fairly regular charter, you will possibly be able to pick out patterns that are 'usual' for you, such as a temp dip before ovulation. It's not something that happens to me, but plenty of women are lucky enough to get that heads up from their chart and you may be one of them!
Your cm should also be taken as a strong indicator of where you are in your fertile window - Have you seen any ewcm (egg white cervical mucous)? This appears for a couple of days before O for most women.
I'd say given your cycle day, and if your cycles are usually pretty regular, then get to bd'ing
Lots of good luck and