Some women get faint lines when they are not ovulating which they interpret as meaning ovulation is coming soon. You don't have a positive OPK until you have a line that is as dark as the test line though. So even if you get a faint line, the test is still negative. You could try using a different brand, such as a digital brand. They are more expensive, but they are a lot easier to read.
Maybe you are testing are the wrong times. Did you get the 20 pack one this way you can check almost every day. You must be ovulating when you don't know it. It's also possible you didn't ovulate this month.
Sorry, I know this is so frustrating but don't give up.
You only see another line when you are close to ovulating. So for example, if you ovulate on day 14, you wont get a positive until cd 12 or 13.