and i am not vaccinated against chicken pox and never had it in my life. How worried should i be?

I went to pick up LO from preschool today and the teacher handed me a sheet on chicken pox info and said there was a kid in the class who had it. It was chaotic pick up time so i didn't ask questions and i wasn't even worried since I know LO is up to date on his vaccines. I figured i can ask more questions in the morning at drop off.

I got home and was telling DH maybe this is not even a big deal, all the kids got chicken pox when i was growing up....then it hit me: except for me, and i never got the vaccine, and i am pregnant.

So DH will do drop off tomorrow and talk to the teachers to get more info and I plan to call my midwife. But i am wondering how high my chances are of exposure if LO doesn't get it and all i did was pick him up today? Anything else I need to think of or do? How worried would you be?