So much anxiety

I’m 15 weeks pregnant. This is my third pregnancy and i have so much anxiety this time that everything is ok. My last doctors appointment they couldn’t find the heartbeat so they sent me for a stat ultrasound. Everything was perfectly fine and baby was moving like crazy and actually measuring a week ahead but ever since then I can’t get it out of my head something could be wrong. Anyone else feel this way? What’d you do to stop the anxiety? It’s keeping me up at night.