Please help, a bit confused.

So I'm in a tight spot, I have 28 day cycle. I track ovulation thru <a href="">glow app</a>. Anywhos my LMP was Nov. 27, on this glow up it states I ovulated Dec.10. So my open fertile window is between Dec.6-12. I had sex with my bf on Dec. 9. And unfortunately went out on the Dec 15 and saw my ex and had unprotected sex that day. I'm so confused as to when I conceived. I took a pregnancy test (dollar tree brand) on the Dec 23. And it came back positive. And Monday morning a Clearblue and it stated I was pregnant. Is there a chance it can be the 2nd guys kid(I tested positive after 8 days of unprotected sex with the 2nd guy.) Please no rude comments just asking for advice thank you.