All of a sudden high risk at 29weeks... Seeing MFM next week.

I've had a normal pregnancy so far. Baby always measured good, heartbeat sounded good, looked good. No GD, no high BP. I am RH negative but I got my rhogam at 28 weeks. Now I'm kind of thrown a curveball, I went for my biweekly checkup and went my midwife checked on my baby girls heartbeat, it was a bit harder to find. The number kept bouncing around. It was making me extremely nervous and she ended up sending me to the hospital to get a NST. When I finally got hooked up, baby girl was soo active and kept moving away from the Doppler. We figured that what was causing it. Such a relief. They ordered an ultrasound and we went down and saw our baby ❤️❤️ I hadn't since my anatomy scan. Everything looked good, no problems. We even saw her practice breathing. My OB was there and discharged us because nothing looked wrong. Next morning I recieved a call I'm being referred to perinatologist because I have polyhydramnios. I knew what this was but was scared because I remember it correlates with birth defects. But our baby has been fine??? I made the mistake of googling it. Smh. I have no idea what it could be. I never measured larger than 2cm on my fundal height. I have some shortness of breath and abdominal tightening/ pain but I figured those are normal pregnancy things. No swelling either. I'm just a bit nervous but hoping it's just a weird anomaly that happened and will go away on its own. Don't you think if it was severe they would've seen that?! I'm so confused. I want my sweet baby girl to be okay 😓 I'm getting an ultrasound and echocardiogram on Monday so I need some good vibes 😞