OPK confusion!

My cycles have been fluctuating between 28-33 days because I'm still regulating from going off the pill.  Since I'm not sure how long it will be lately or when I will ovulate I've been taking OPKs starting on CD10 to be sure I catch it.  Yesterday was CD10 and I got a negative but then today I tested and got a negative still but with a fainter line.  Shouldn't it be getting darker as my O day gets closer?  Or is it typical for hormone levels to go up and down except for the spike on Ovulation day?  I haven't been using my first morning urine but rather catching it in the afternoon when I get home from work, can my fluid intake mess with it?