Paternity help 🙏🏼

I have spent a lot of time thinking about this recently, and I just need someone to ask about it! I’m concerned about paternity, but aware I could be being a little irrational about it.

On Nov 8, 2019, I found out I was 5 weeks pregnant. (Give or take a few days, they said.) I had been back together with my boyfriend since August 29 and since Aug 29, he was my only sexual partner.

The last period I had logged/could remember was September 5, and I didn’t remember having a period in October. However, being 5 weeks pregnant on Nov 8 meant I would have become pregnant the first or second week of October.

Between early July and late August, I was with a different partner than my boyfriend. Anyway, I only have one ovary which means I have my period from that same ovary every month. When I got pregnant, i was both on birth control (body was adjusting to a new kind) AND living with one ovary and so the fact that I got pregnant at all was pretty mind blowing. I guess it’s made me feel like anything could happen and I have this fear in the back of my head that the boyfriend I got back together with could somehow not be the father. I know it’s possible I just don’t remember having a period in October or that it was pretty light, but just need some affirmation.

Any thoughts? Is it even possible it’s not my boyfriends?