My heart rate...

So I know they say your heart rate increases in pregnancy. So anyways I have the Fitbit with the heart rate monitor. And last night while sleeping it went down to 44 it was around 2am. Right now it's like 68. I am a very active person ran 6 half marathons and I'm trying to get back to the gym but the exhaustion and morning sickness is making this hard. Should I worry?