After DS and a 2nd degree tear, the doctors and the discharge instructions said to wait 3 weeks. When I asked my doc, she told me that she would recommend 6 weeks because mentally most women just aren't ready, but that medically 3-4 weeks was all I had to wait.
DH and I had sex at 7 weeks last time, and 6 weeks this time (no tear!). Just take it slow and use lots of lube. It hurts much less then a pap and a lot less then getting an IUD. (or birthing a baby for that matter.)
Just give it a try!
I'm at 5w PP and don't feel near ready. Plus I'm just exhausted right now.
ETA: My MW's say 6 weeks.
Got the clear at 6 weeks, had a 3rd degree tear