I'm using OPKs from eBay, the Australian ones that come up at the top of the search ("yes.bw" seller) and have not got a positive result this month. I normally ovulate on CD16 (which is today) and have a pretty regular 30 day cycle. I used them last month and got positives on days 14-16 but testing several times per day I got widely varied results - strong positive, then only a faint line just a few hours later. This month I got a faint line on day 14 and 15 (testing 3-4 times per day to be sure I don't miss it if it's quick), now back to no line at all. It seemed like I had a surge but it wasn't high enough to register as a positive result. Has anyone experienced this with these tests? Is it still possible I'm ovulating or would you assume I still haven't ovulated?