ultrasounds need opinions and help

My ob loves doing ultrasounds, she says it's the best way to check if everything is looking good and healthy, I'm 33 weeks an she's done about I think more then 6? My doula says that's not really a good thing, normally people get 2, unless they have a high risk pregnancy they'll get more, but I shouldn't be getting more. I've just heard not great things about getting them all the time, now I'm paranoid! Does anyone on here know more about effects it can cause?