Eric is watching them intently as Pam feeds.
At first, his only thought is concern for Pam's well being (and thus, relatedly, Jemma's).
But as Pam's skin begins to knit and her movements become more sure, he allows himself to enjoy the scene as well.

They do look very pretty together.

And all the while, he is listening to Jemma.

Just a little more, just -
"Pam."

It's said gently and with more emotion than he probably intended, now that they have company.
It still means stop though.