I don't think having a C-section has anything to do with it. I had one and my doctor recommended 6 weeks (and I happily complied). I was in no condition physically to have sex before that mark. It is a surgery after all...
Married Bio * BFP Chart
That's just crazy. The main reason doctors say 6 weeks before sex is due to risk of infection due to the open wound caused by the placenta. For me 6 weeks was too early due to the episiotomy and horrible hemorrhoids. It was probably 8 weeks and it was still painful. It took a few months before things were back to normal.
I cried at my 6 week PP check up when they told me I could have sex again. I seriously thought about lying to my H and telling him I wasn't cleared yet.