Is it strange not be pregnant after a year?

Is it strange not be pregnant after a little over a year of unprotected sex? My husband and I have never used any contraceptive or anything like that since we have gotten married (Feb. 27, 2010) and we had been having sex before that unprotected also. He keeps asking me if I might be pregnant when I'm late, but I always start after he asks (weird I know)...but I've never gotten pregnant nor have I ever miscarried or anything like that...I have missed a couple months here and there, but any test I've taken has always come out negative....so I was just wondering if it was strange not to have gotten pregnant in a little over a year of having unprotected sex....