Sinus tachycardia

I was just diagnosed with sinus tachycardia today. I am scared that I will end up delivering early because of this. I am currently 27 weeks 2 days. My ekg showed a normal rhythm but very fast. My dr said he is consulting a high risk specialist. Anyone go through this before? I am trying so hard to not let my mind wander and think horrible things might happen. Any Advice is welcomed. Also I do not drink anything with caffeine and I have only gained 17 pounds so far.