omg what have I done

so today is 33% chance of getting pregnant and I had sex with my boyfriend but he pulled out before could i still get pregnant but we are not planning to get to have a baby but I mean if it happened I would be so so happy and I would try to be the best mum I could ever be I already know the answer but just wanted to hear another person advice or if I could be and also my brothers girlfriend has just came out that she is pregnant and they have been trying for a year now and I dont want her to think I'm trying to compete with her so can someone help