baby's heart rate question

Vivian
So I have a home Doppler to check my baby's heart rate when i want to. I usually check it once or twice a week just for peace of mind. 
I checked it this morning and it was a normal 149 like it usually is. But then I had some abdominal pain earlier today so I checked it again and it was at 131. Is that normal? 
I'm not the best at checking it since I'm not a trained doctor or anything but that's what it stayed at for a few seconds. 
I'm 19wks2days.