Confused?! Please don't judge.

I made a careless mistake by sleeping with two different people 2 days apart and now I'm pregnant 😫. My last period was Nov. 11, and it's regular and lasts 4 days. I had sex Dec. 6th and Dec. 8th.... On Dec. 19th. I had sex again and it's was the most painful sex I've ever had, which was weird because I never cramp like that after sex. So anyways, after that I started feeling really ill and extremely exhausted, and my sister encouraged me to take a test. And of course I did thinking nothing of it. And bam! Big fat positive! That day was Dec. 24th
So, Jan. 3, I went to the doctor and was told I was 6 weeks exactly...  Then I went back on Jan. 5 because I was told I had a hole in my cervix and to come back, and I had another ultrasound and was told I was 7 weeks and 3 days, and they said the measurements I the baby coincided with my lmp. But that would've made my conception date Nov. 28, but I never had sex at all in November. So I'm very confused. Can anybody help with guessing which day I most likely conceived.