I have used withdrawal method for almost 10 years now with my hubby.
Dec 2011 was the only time it didn't work for us and I ended up pregnant.
I think you have to still be mindful of ovulation week and be extra careful!
I remember saying to hubby before DTD that I was extra slippery tonight so no stuff ups cause I'm fertile mertile! His response was a laugh "I'm pro by now hunny!"