Thoughts? Failed birth control

I was on birth control and it somehow failed and ended up pregnant. I had sex with my ex three time august 6 10 and 14. He never came in me always pulled out. August 1, 2 and 8 and 20 I had sex with someone I’d been seeing for a bit and he always finished in me. My last period was July 24. What are your guys thought on who’s it is with out being rude would be great. Thank you. I was on the pill and tracked my ovulation. Every ovulation test I took when having sex came out negative so I’m just as lost as to when I could have conceived. I found out I was pregnant on august 22. I had took two pregnancy test somewhere around august 15-18 cause I felt weird but they came out negative.