I asked my Ob at my six week checkup and he said whenever I felt comfortable. This recommendation likely varies depending on the woman and her age/recovery from surgery/overall health so I think you should talk to your ob.
I had no problems being pregnant and caring for an infant. The scar tissue healing wasn't a factor and my second pregnancy was easier than my first. I think being pregnant with a toddler would have been a whole lot harder honestly.
I do think you should stop having unprotected sex and talk to your ob. It is possible to get pregnant while breastfeeding and it's not worth risking your health over.