No, it's not too late to chart. I do know of some women who don't log their temps during their period (or what we affectionately refer to as AF), but I would suggest you temp during this time anyway, just so you're in the habit of taking your temp every day at the same time. Have you checked out
www.fertilityfriend.com? The site is chocked full of great articles on charting, how to chart, etc. and you can plug your temps and other vital info right online for a comprehensive outlook on your cycle.
You will notice that FF has message boards as well, but you now have to pay a membership fee to obtain access. Since I don't believe one should pay to have access to boards, I went researching online and stumbled across this board - I think you'll be as happy with this site as I am.
And no, there aren't any stupid questions. Good luck!