Unprotected sex 3 weeks after giving birth

Now before anyone jumps down my throat I wasn’t aware that you weren’t supposed to have sex for 6 weeks & until your check up. No one told me, not drs, not family, no one.

After 9 months of not worrying the hubby and I didn’t think about contraception which is my own fault.

The reason I’m posting is

1, In the case of an infection what am I looking for, signs & symptoms ? As I’ve tried to google it and haven’t found anything.

&

2, I’ve seen very contradicting posts about fertility after giving birth. Posts either saying “yes you’re very fertile” & “no you don’t ovulate till 90 days after giving birth” which one is it ? Has anyone gotten pregnant in the 6 weeks after giving birth?