Now I'm all worried even though I shouldn't be?

I had my appointment with the obstetrician today. When he was doing the sonogram I couldn't really see the heartbeat (could have missed it) but when he used the doppler he found the heartbeat after tracking it a bit (he said it was moving a lot) with a heartbeat of 160bpm. Now I'm all edgy at the back of my mind. I'm 20.5 weeks already.