15 days late, 2 negatives and spotting

Hi everyone, I need some inputs... According to my app. today is my ovulation, but my period supposedly to come on 9 Dec 20, never turn up. My last period was 11 Nov 20, so I am now 15 days late. I did 2 pregnancy test last week on, 14 and 18 Dec, both showed 'Negative'. I had some spotting on 20 to 23 Dec, dark brown. And I don’t feel any symptom of pregnancy Since the app says today is my ovulation, do I have any chance to get pregnant if I 'marathon' tonight? Although the December period never come?? I am dilemma, been trying hard for the past 16 years.