I would agree with the other posts, that you are ok (the baby is ok) Of course, none of us can replace an OB, but I have heard of and read of this happening and everything was fine.
This may not ease your mind at all, but I wanted to let you know that there are many times fears can be unfounded. My hubby and I were done having children and I went on a mission trip to Brazil. In the months before the trip, I was getting different vaccinations - yellow fever, hep A, etc. I also took Malaria pills while in Brazil. When I got the injection, the nurse told me not to get pregnant in the next 3 months. I chuckled, and told her that was not a problem. Well, since there seems to be NO birth control that is effective for us.....I was pregnant within 2 months (or so). I had to have more workups and tests throughout the pregnancy, because I was ALSO considered in the advanced maternal age!! Talk about nerve-racking!! My little girl was born perfectly healthy - in fact, she is so smart and bright, it's scary. LOL!!
I'm sure you have (or will) mention this to your OB, but if I were you, I'd try to just relax and put it out of your mind. I know that's hard to do, but I am confident your baby will be fine :)
Congratulations, by the way!