38.2 & worried! 😰

Over-anxious FTM here, due 10/3! Any advice appreciated.
Throughout this entire pregnancy, baby's heart rate has ranged from 148-158 and my blood pressure has ranged from 110/60 to 111/72 ...
Well this morning I had a Drs appt (non OB) and my BP was 138/78, which concerned me as it's never been that high (though I realize that's not "high" by most standards). I called the OB, concerned and they saw me today.  He said I seem fine and it's not pre-e, then he listened to the baby's heart rate.
He used the Doppler but he didn't move it around that much (other OB's in the practice usually move the wand around until they find the strong heart sound) and he found a very faint beating sound and went "sounds like 134 to me."
Does the baby's heart rate drop significantly before labor??? OB doesn't seem concerned with this heart rate, but for weeks prior to this appt, the heart rate has been consistently 154 and this seems like a significant drop to me!
Am I just freaking out over nothing? I feel worse after seeing the OB and haven't been able to concentrate at work all day, worried that my baby is in distress or something! 😩 Baby is moving - not as strongly as before, but I know that there is less room in there as I'm late in my pregnancy and baby is allegedly 8+ pounds right now. (Eek!)