Calm my fears?
I'm totally with you. DS was a high needs baby (was awake all the time from a few days old, nursed for hours and hours at a stretch fussed and cried a lot. Not sure he was colicky per se, but he definitely put me through my paces.) DD is now 3.5 weeks and is calm, sleeps lots, nurses well but not constantly. Like you, I've been waiting for the axe to drop. But, as Melly has pointed out, babies can just be different.
If she does start getting "colicy" at this point, it would most likely be due to a food sensitivity. My ds2 got more and more fussy as we approached 3 months, instead of better. But once I eliminated dairy from my diet, he was sweet again after 2 days. Most food sensitivities in babies are dairy-related, so it's a good place to start if you run into trouble. I am telling you this in hopes to alleviate your worries. If your dd does get fussy, there will likely be a pretty straight-forward solution. I find it easier to dismiss worry and anxiety if I have a plan in place for the "what ifs," so I hope that's helpful for you, too.
I understand your worry, though. Ds3 had a chronic cough/congestion his first winter, so I am watching ds4 really closely. I've had a lot of worries about going through that again. BUT, then I remind myself that now I have access to a wonderful homeopath now, and we will most likely be able to nip something like that in the bud before it gets bad this time around (homeopathy cured ds3, it was just a few months of a very difficult time before we consulted her last time around, as I was just beginning to learn about homeopathy).
Have you looked into some nutritional supplements for yourself to help reduce anxiety? I would start with Floradix for iron (fatigue can contribute to anxiety) and fish oil for Vitamin D and omega 3s.