What Causes Throat Pain And Appetite Loss In A Child?

Hi - I have a 5year old daughter who won t really eat anything and has to be forced to eat, she complains that her throat constantly hurts, she used to vomit a lot but I ve cut down on her milk which has helped abit, she gets tired quickly. She looks ok but I feel she looks skinny compared to my other children. Are these symptoms anything to worry about? Thank you