Is increase in heart rate on FitBit a sign of early pregnancy ?

Hi Ladies,

My husband and I had our first cycle of TTC this month after a missed miscarriage at the end of May. I ovulated around the 18th and we made sure to BD every day leading up to ovulation. I’m supposed to be getting my period on Friday, 8/2. I don’t really feel any PMS symptoms, except for being more emotional than usual. I’ve taken 3 pregnancy tests since Friday (I’m nuts, I know). They all came back negative. I’m noticing that my resting heart rate is elevated on my FitBit, though. I did a little (ok a lot) of Googling and saw that for some people an elevated heart rate was the first sign of pregnancy. Does anyone know if this is true?