If only breastfeeding was the magic bullet that would keep kids from getting sick! But it's just not. Nothing can stand up to the assualt of vicious germs that come from daycare (or preschool, or kindergarten). The only thing you can be sure of is that if your baby wasn't breastfed, this situation would be so much worse.
Has baby been thoroughly checked for bacterial infection? If some non-standard strain of bacteria is making your kid sick, and the usual antibiotics aren't knocking the infection out, maybe a bacterial culture would help you find the right antibiotics for the job.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"