Dna testing

So I’m in a dilemma. I was with my ex for 4 years having unprotected sex at least every other day that whole time up until we broke up in early November. We did have sex the first week of November. I had sex with another man after we broke up on November 22nd. I’m 13 weeks pregnant. Wouldn’t I of already of been pregnant when I had sex with #2? I’m going to get a dna test when the baby is born it just sucks not knowing.

Also I didn’t have a period at all in November it was the end of October and my ex and I had sex again around Halloween