Slow pulse 6 days pp

I had a pretty intense labor and my baby has been in nicu since he’s born. It’s been a really high stress time and I haven’t been able to sleep or rest. My pulse has been lower 50s resting even going to 48 at some points and walking it’s

In 60s. My dr said anything over 50 he isn’t concerned but I keep taking it over and over and it’s been 48 a lot. I’m freaking out and feel sick from stress of everything. Someone please tell me this is normal. It’s 1am I’m exhausted and can’t sleep bc I’m terrified. I do have an apt with him tomorrow but I need some piece of mind so I can fall asleep and recover.