Question

I had sex the 10th (day before ovulation according to the app) and the 19th. My period was due according to the app 3 days ago. And I tested negative today. What should I do? Am I out? Or could I have conceived on the 19th. My periods have been irregular since having my son last year. I don’t breast feed and on no birth control either. I get frequent ultrasounds for the cysts on my ovaries. And I went on the 21st and she said they looked perfect and there was a visible dominant follicle. No cysts. So I mean I’m confused as to what could be delaying my af. I’m not stressed so whyyyyy lol any input would be great I’m losing my mindddd