Stressing...

So this Wednesday we have 2 ultrasounds. One we are paying out of pocket to find out the gender. There is a place near me that can tell as early as 13 weeks. The other ultrasound is for NT testing. I had a regular check up with my Obgyn 3 weeks ago at 10+3 and the doctor didn't get the heartbeat on the Doppler (we saw a heartbeat on ultrasound twice) when she tried. She told me not to worry bc it was early. Yea...easier said than done!!! Well ever since I have been stressing that something is wrong. I haven't had any bleeding or cramping and have still gotten morning sickness aka all day sickness. So all signs point to everything is okay but yet for some reason I'm freaking out. My husband thinks I'm nuts and doesn't understand how i can't just relax. I've heard of "missed miscarriages" before and that's what scares me. That the baby could stop growing and you have no signs of anything being wrong. Any advice in how not to worry or any encouraging words to help this mama get through till Wednesday???