Ovulation Test

I was hoping y'all could help me out a little bit. I wasn't sure if I was wanting to use ovulation tests this cycle and decided kind of late. I took my first one on cd 13 I'm now on cd 18 and have gotten a negative test every time. I use a digital reader but always stop to look at the tests afterwords well I've noticed the line get light everyday since the first time I tested. So my question would be does anyone else thing that maybe my peak day was cd 12 and I ovulated in cd 13 when I took my first test?

I'm posting the pictures of the first test compared to today's.