So Glow said I was supposed to ovulate today. Yesterday I took a test and there was a faint line. I know it's upposed to be as dark, or darker than the control line so I just threw it away. This morning I tested again and still just a vvfl. Are ovulation days usually constant? Or can they change?? Because there's no sign of ovulation but I've never had any problems with my period or inconsistency.