When to Test ?

AF was supposed to come on the 13th I had spotting really light on that day maybe for about 3 days very very light enough for a panty liner only. No cramps no mood swings nothing everything was normal except I have sudden urges to pee all the time very frequently I took a test on the 19th it was negative. When would be the best time to test for accurate results I know my body is off my periods are very regular and Often heavy something's not right but I can't pinpoint it .