Can someone please help me understand?

Melinda • Had 4 miscarriages in 2015 and had our rainbow baby December 2016
I usually ovulate on cd 12 which would have been last Saturday May 2nd. My husband and I went away for our anniversary so I wasn't good at taking my opks when I normally do. I did take one Saturday and it looked almost positive like the picture below but didn't take another one later and I then took another one Sunday and the second line was almost not there so I assumed I already ovulated and that was that. Now I took this one and it looks almost positive again. What is going on? I'm now cd 16 (would normally be 4 dpo). I'm pretty new at opks so please don't bash me. I'm just looking for some answers and I kno you women are great.