I stroke the 4-week-old’s cheek. I did it to her sister (now 7) for the first couple months, too.
This afternoon I had ‘babysitting’ duties while my daughter had an appointment with the hairdresser. Babe is 5 weeks old and just stayed sleeping on my easy-chair wrapped in his blankie.
I poked him every few minutes! It’s great fun to see them squiggle and make those funny mouthie-face things. He did stay asleep of course, what a brilliant baby!
See…even nanas do it too. 
I do this to my husband, too. It’s why he hates that I also poke the baby. I can’t help it! They both sleep like cold, dead things!
My daughter is nearly 10 months old. She was premature, so didn’t come home till she was 5 weeks old, and in hospital she’d sometimes stop breathing for a bit and go blueish, with attendant alarms etc. She’d almost always “self-correct”, but the nurses had to give her a bit of encouragement now and again.
So you can imagine, when she first came home I was lying motionless in bed for hours, listening for the sound of her breathing in the Moses basket beside me. For a good few months I’d get worried when she was asleep and have to go and check on her. And just for balance, I was the worrier and I drove my wife crazy!
Now, though, it’s such an achievement to actually get her to sleep that I just go to sleep myself. Seriously, soon you’ll stop worrying about this and start worrying about lots of other things instead…
Ditto (though my kids are even older than yours… I doubt the college dorm would let me in just to make sure my son’s still breathing :p).
Dweezil was an awful, AWFUL sleeper as an infant. Screamed 24/7, would not sleep unless breastfeeding, we never could figure it out. Finally I “ferberized” him at about 11 weeks. By the 3rd night, he slept 6 hours in a row. Of course at 5.5 hours I woke in a blind panic and ran into his room to make sure he hadn’t died (that being the only logical explanation for the lack of earsplitting screams)… which woke him up :smack: :p.
I think you’re supposed to text him for that.
Perfectly normal to do that, I still go in and check on mine, once they’re asleep.
You never stop worrying it’s part of being a parent I guess.