Heart rate above 180...

Has anyone gone in for their check up and had the baby have a high heart rate?

I'm about 36 weeks now and I went into.my check up today and the doctor said the babies heart rate was really high. So I was told to get a nonstress test done. I started with just being there for 20mins but his heart rate didn't change but maybe once. He was really active,but he is always active, and the only times his heart rate would calm is when he was chillin for about a minute but then he'd go back to being active, which would give him a high heart rate. At one point it went passed 200! They made me drink water and I sat there for about 45mins and they said I could go home. They said since he was able to calm his heart rate a couple of times that he's ok?

Has anyone dealt with this? They didn't seem to worry but they didn't give me an ultrasound or anything so I'm sort of worried.