TSH level of 0.01 (thyroid)

Today I had a follow up with my GP due to a consistently rapid heart rate (100-130 bpm). My bloodwork came back showing my TSH level as 0.01. I see the normal range is 0.4-4.0 but my doctor didn’t seem overly concerned about it. He just said to drink more fluids, especially Gatorade for the sodium and electrolytes. I have another round of bloodwork in 10 days to check. Anyone else have this low of a thyroid level in pregnancy? My dr seemed to think this is super common.