Chances of being pregnant?

Okay... This is embarring, but I'm worried about it. My husband and I are newlyweds, and we didn't have premarital . He got a vasectomy over a year ago, but hasn't gotten his sperm tested yet to make sure he is now infertile. We decided to have anyway, and he pulled out on time and didn't in me at all. We've only had the one time because he has either been gone because of his work, or I've been sick or on my period. The timing has sucked for us... Anyway, I do NOT want to ever, ever, ever have kids. That would be one of my worst nightmares! I haven't been having any weird symptoms, and we had about a week ago. My period is due to start around the 12th. I got some pregnancy tests, but it's still too early to use them. I was wondering, though, is there much of a chance that he might have gotten me pregnant?