Don't know how to confront my guy friend?

So I've been friends with this guy for over 3 years now, he's my ex boyfriend's best friend ( confusing I know, but I'm friends with my ex so it makes it a little less weird) But my guy friend recently met this girl and they've been dating for a couple months, I like her, she's nice, and quiet. BUT I don't like the way my guy friend acts now that he's a boyfriend, he's completely sullen when he's not with her, he full on POUTS, and when he is, he won't stop doting on her, making sure she's warm, making sure she has food if she's hungry, I wouldn't put it past him to check her pulse to make sure she's breathing. I feel awful because I should be happy for him, but I can't stand him when he acts like this. How could I possibly confront him on this, and should I?