Did pull out method work?

Hi, I’m not trying for a baby but I’m also in a position where I want to start thinking about having children. On my ovulation day, my partner and I had sex and he pulled out, but I’m not sure if he managed to time it all properly as when I went to the toilet half and hour later, sperm came out in my urine. We also had sex again the next day and the same thing happened. May sound like a stupid question, but what are the chances of becoming pregnant from only a very small amount of sperm?