Hiya, i haven't read the other posts, so sorry if i am repeating what has been said.
The chances are pretty slim TBH. Even slimmer if you are exclusively breastfeeding! For the purposes of this answer i will just assume that you aren't breastfeeding and so could have ovulated.
1. Your body takes a while to get back to normal after giving birth - for all the hormone levels to get back to the correct place to be able to kick out an egg.
2. You would have to have had your oopsy within the 5-7 days leading up to ovulating, the day of ovulation or the day after (although the day after is not great for conception).
3. To get pregnant from the withdrawal method the guy must not have pulled out in time, which you have explained is the case for you. If the man actually DID pull out in time there is very little chance of getting pregnant from the precum. Sperm can live in precum, but only if they are sitting there from a previous ejeculation. The guy must have masturbated, ejeculated and not urinated before having sex with you - leaving sperm sitting in the "pipe" surviving in the precum. The precum comes from a completely separate place to the sperm.
4. If he didn't pull out in time and a small part of the semen went into your vagina then that's only a fraction of the millions of sperm that usually get in there.
5. If everything goes perfect for conception - right days for ovulation, nice big ejeculation in the right place etc. then chances of conception are only about 20% per cycle anyway. So as you can imagine, if anything is less than perfect - not a full "load", too many days before ovulation etc. then the chances get slimmer fast.
I hope this is reassuring for you!! Good luck either way.