Resting heart rate

Does anyone use a heart rate monitor (like a fitbit)? I'm only 5 weeks but I knew early on because my resting heart rate kept climbing when it would normally decrease about 3 days before my period would start. So far it's increased from 61 to 72, but I just noticed this morning that it has slightly decreased. Just wondering if this is normal or if anyone has experience with what I should expect with my resting heart rate...is it normal to go up and down? I expected it to level off but not decrease..

#Concerned 😕