Excessive Worrying

My daughter is 9 and not diagnosed. There are lots of signs and just wondered if anyone had any experience. She cries every night and morning about going to school but when she is there she masks most the day. She worries excessively about getting ill every little thing she says is it normal? Will it become infected? She has learnt about disabilities and allergies and says things like what if I have one? It is so difficult and tiring I don't know how to help and support her.