I hate to call the OB...

I hate to call my OB office for every little thing so maybe just some input or experience from someone else would ease my mind. My heart rate has been really high lately. It's not all the time but I'll be sitting on the couch or out an about and all the sudden feel weak and my heart will race. When I check my heart rate with a monitor its around 115-120 which I know is high. Is this normal? I had a perfect pregnancy with my son and this one is completely different.