I'm 12 weeks pregnant and I had an Xray of my pelvis before I knew I was pregnant. I was told that Xrays have an all or nothing result. If it did damage, you will likely miscarry not long after and if you didn't/don't than everything is probably fine.
One Xray probably won't harm the baby but definitely mention it to your doc so that when you have your ultrasounds they can check a little closer :-)