Well, my DD is was and still is a fussball. I was complaining to my 88 year old Grandma one day, and she said, 'Well, she's a baby! What do you expect?!" I don't know about your son, but for me, BOTH my boys were easy going as newborns, and adjusting to a new (fussy) baby can be hard, but think of it this way: she's been alive for a month...give her time to adjust to the world before doing all sorts of stuff. Take a deep breathe when she's getting under your skin and stay calm. It'll be a quick hump to get over. Colicky is upset ALL the time, and if she's not in that category, just try to bear with her.
P.S. My baby gets better a little every day. I think Addy will, too. Good luck hun.