HCG trigger shot with OPK question!

Hi!! So we did 5mg of letrozole CD 3-7 this cycle with trigger shot at midnight on Sunday night. I had my first solid positive OPK (first one in the bundle of 6 at the botton) at the time of the trigger but I decided to use it anyway (5,000 iu). The next morning (Monday) I took an HCG test and it was negative. But I did have 2 more positive OPKs (really dark ones at bottom) that day and then they began to get lighter last night just slightly (urine could have been a bit more diluted, only 2 hour hold).

Then this morning with FMU (bottom one) it's clearly very positive today. 36 hours from my trigger would be today at 12 noon. So I should ovulate today. Just wondering if its normal to have another dark positive OPK 24 hours later from the first very dark ones? Also, I never had a positive HCG test after the trigger? Maybe my body just didnt accept it.

Has anyone had a similar experience?