30 weeks Rapid heart rate...

Hi ladies! So today I woke up had normal brekkie, cereal with almond milk and then washed dishes n started prepping for later so was quite busy! Shortly after brekkie I noticed mybheart rate elevated but I noticed it only cus i felt anxious out of no where. Checked (I own a pulse oximeter) and heart rate at highest, went to 145 but didn't stay that elevated... Fluctuated for abt an hr between 100-125. I am 30 weeks pregnant and it did worry me but I also read it could be normal???