Allergies or Not?

I am hoping some of you that read this, mainly the mommies can help me out.
You know I have been dealing with roo being " sick " for sometime now, all winter it would seem and things arent letting up.
I am wondering if maybe these fevers, which seem to come on so fast, and hang around for a few days even despite tylenol and whatnot are related to allergies?
Lastnight her nose started running, and she was again throughing up this nasty flemish crap. Its pure goo nothing else. And she gets so misserable.
We didnt sleep at all because she didnt unwind, and then she hasnt eaten in ( today will be 4th day ) 3 days. Shes just not hungry, who would be with all that goo?

Do any of you have any advice, tips thoughts to share regarding this?

And .... Do you think its possible its the pediasure ( if she has a milk allergy - causing some of this ) Seems like nothing but troubles since we stopped nursing, went to formula, and then to the pediasure.
GRRR.

Frustrated that my baby doesnt feel well.