Any advice?

Hey everyone! Hope your all having a wonderful night!
My periods are a bit everywhere at the moment. Iv been TTC for 16 months. I was using opks to find out when I was ovulating. 
I ovulated on the 25/2 according to my opks. 
I was expecting my period Thursday which didn't turn up.i took a pregnancy test and it was negative. 
I used an opk on Thursday night (if drank a lot of water) and the second line was quite dark,nearly as dark as the control line.i have tested using a pregnancy test today and it was still negative. Used another opk and this was my result.. Any idea what's going on???