Issues with racing heart beat while prego.

So I have been having issues with my heart racing for the past 2 wks. (I have called my doctor).. I just want to know if anyone else is experiencing this kind of issue. My heart races for about 15 to 20 mins. I'm always in a calm position when it happens.. at hm watching tv or at work on the computer. It feels like I'm having an anxiety attack and I can't breath with a feeling of breathlessness. Kinda like I ran up the block and back or ran up a flight of stairs. I have done my glucose testing and everything is normal. It's only a handful of times, and it didn't happen with my first pregnancy. So this is something new for me if it's normal. My doctor says that if it happens again to go to the hosital ER, but shit by the time I get there checked in and stuff it done went away.. I wish I had a blood pressure cuff to take record of when it happens, but I don't have one. So please give me some clarity I don't want to worry if it's just some weird pregnancy symptom. I'm getting it taken care of, just curious.