We have been consistently sick with one thing or another since before Christmas. One kid gets well and the next one gets sick and so on. I don't take my kids to the dr unless they complain of their ears hurting or if the fever isn't gone in a week or so. I usually just put a call in to the nurse if I think they may need to be seen and she guides me from their.
I think you need to get a handle on your anxiety. Your kids will pick up on it. Kids WILL get sick, they just do. And you need to find a way to stop worrying about every little sneeze, sniffle and fever. If they never got sick their immune systems would never get strong!