I read somewhere (I think it was in Gale Bernhardt's "Female cyclist") that most people need more calories in the week leading up to their period. That seems to be true for me, so if I have a race coming up and am at that time of the month I make extra sure that I am eating properly and am well hydrated.

I can sympathise about getting hot and cold - I certainly get hot and bothered very easily and often don't feel like training but once the start gun for a race has gone I'm usually ok (must be the adrenaline) - at least this has always been the case with rowing and ski races so far.