Nothing to Worry. Repeated ultrasounds have never been demonstrated to increase the risk of autism.
Don't worry. There is no good research that supports the link between autism and fetal ultrasound. Many people have great personal investment in "proving" links between autism and something or another but they have not been proven to be true in real scientific research projects. If you had so many ultrasounds there must be a medical reason that your doctor ordered them. Ask your doctor why.