Couldn't find a heart beat at 19 weeks.. Very worried

Went to my appointment this morning with my new Dr. (Switched because the last one sucked) and she tried to find the baby's heart beat because my last Dr didn't even try and I really wanted to hear baby because I haven't even felt my baby move yet. And i dont have a bump yet either, my tummy is just less soft below my belly button.. She couldn't find it after 10 minutes of trying. I heard mine, and a whooshing noise that she said was movement. She didn't seem too worried about not finding it because of scar tissue from 2 csections and having my appendix removed. Or that i ovulated later and am not as far along. But then i would only be like 3 weeks less pregnant and should still be able to hear something right?? And She also said you can't hear anything through scar tissue. Idk tho I'm very nervous. Going for my first ultrasound with this baby next Wednesday I'm so scared that there will be no heart beat or something is very wrong with my baby :'( please tell me someone else went through this and their baby was just fine.