Ovulation

So I've read plenty of posts about how having pcos can mess with ovulation tests because the levels appear to be high frequently or at more than one time. But I was wondering if the opposite could also be true?  I'm new to the ovulation test thing. I'm on cycle day 13 with an average 30-31 day cycle. I've taken two tests and both have come out with no second line. Or possibly a vvvvvvvvvf line. I'm going to wait two days before taking another one. I am on metformin for insulin resistance. My doctor hasn't technically diagnosed me with pcos but she said it sounds like it could be. Any thoughts or advice on the tests?