Hi lil mama. You prob should be in the Pregnancy forums, not Breast Feeding.
Anything is possible, but why are you already having sexual relations?? My baby is almost 4 months old and we didn't even think about sex till prob a month ago, when the baby was 3mo. Your body hasn't even healed yet inside, so it's not a good idea to be having sex. This is why the Dr prob told you to wait 6wks. Breast feeding is not a form of contraception. Good luck to you, and congrats on your baby.
The chance is very small, since you are likely still bleeding from giving birth and/or just stopped bleeding. BUT i agree with the above post, really, it is too soon to be having sex. Let your body heal first.