How and when?

I got peak/flashing smile on the 16th and try again on the 17th but appeared low fertility? I don’t know how it happened but then I had sex on the 21st yesterday and got flashing smile and now while I’m washing mine there’s a clear egg white discharge and I tested and got steady smile/non flashing smile but no sex. I’m confused how did it happened? Like got flashing smile then next day disappear then after4 days got flashing again and today got high fertility?? Can somebody explain it to me?

Thankyou