Usually a day before ovulation, the level of luteinizing hormones (LH) in the blood/urine rapidly increases and decreases. Ovulation sticks detect and show this peak in LH-levels as a "line" on the stick which, when compared with the control line, is either the same color or darker than the control line. Because there is always some LH present in the blood/urine the ovulation stick will always show some variation of a line on the stick. But if there is no LH peak, this line will be faint, compared to the control one. So, it may be that you are not ovulating during your period... but the ovulation stick is detecting a small level of LH that is lower than the LH-levels just before ovulation. You can follow up with a gynecologist to verify if, indeed, you are ovulating, or not. Lack of ovulation indicates an abnormality in the reproductive process.