Look for a hair wrapped around his finger or toes.
Put him on yours or your dh/so chest and put his head in the curve of your neck and hum a song, or just a calm rhythm, in a low voice.
Check his diaper again.
Give more milk if its been 2-3 hours or usually length of feeding time.
Walk around while holding baby.
If it gets too much, put baby down somewhere safe, like crib/bassinet or playpen and walk to another room and breathe deeply for a minute or two. Maybe even scream into a pillow if needed.