Should I be anxious?

I just saw my obgyn for a follow up re:my ultrasound. She said they requested a follow up as they might have found something above her heart and want a closer look. They are referring me to the sick kids hospital and not where I got my ultrasound. I'm 24 weeks. My daughter's heart beat is strong and she is kicking regularly. My obgyn doesn't think I should be worried but I can't shake it. Anyone have a similar experience?