How long should I wait to take a pregnancy test??

I am on a 24 day cycle and I read somewhere that you need to wait 4 to 5 weeks to take a test. I started charting my cycles about 4 months ago, and I am VERY regular. I get it on day 24 like clockwork. Well, today is day 24, and Aunt Flow hasn't shown up, and it doesn't feel like she is coming. (I can usually feel her coming the day before). I urinate almost every 1/2 hour, and I feel nausious. I toold a test this morning and it was negative. Should I wait a couple days??