If the line is feint it's usually negative. With OPK's it's only positive if the test line is as dark or darker than the control line. For me, I didn't find they got progressively darker as I got closer to O. I also found that charting my temperature helped pinpoint ovulation because until I got used to them I found OPK's quite hard to interpret sometimes. For a 28 day cycle I would start testing around day 10 just in case you O earlier than the normal day 14.. GL