2 Potential father's...

Just wanted to have a brief discussion on the topic and am in an uncomfortable/stressful situation. Honestly, i need reassurance. I am 32 weeks pregnant with my son and even though I believe my long term partner is the father of my child there are doubts, I can't be 100% certain that the child is my partners so I suppose its only natural to worry. Anyways, my partner and I had a brief seperation in the very beginning of January. I ended up having unprotected sex with a very close friend of mine at the end of January, the night of the 27th to be exact. I took an ovulation test on the night of February 3rd and it came back positive. After everything, my partner and I had decided to work things out and before all of this we were trying to have a baby for months. He knows everything, we've obviously decided to leave the past in the past and stick it out and he is 100% certain that this is his child based on his own research and has tried to reassure me that the chances are very very slim. From the 28th and then on my partner and i had unprotected sex countless times, we assumed i would be ovulating soon and we were correct in our assumptions and when I tested positive on the 3rd we had unprotected sex multiple times to ensure I would conceive. I've read a lot about conception and how sperm can survive in the vaginal tract for days in the right conditions, cervical fluid etc.. I've gotten varying answers on how long sperm can survive in the vaginal tract. At the least there would be a 6 day gap between the time I had sex with my friend and when i ovulated, and at the most 8 days... what are the chances that my friend could be the father of my son?