why won't my turtle eat?

by Veronica
(New York )

so I have had my turtle for some time now. It is doing something it had never done before.My turtle refuses to eat, I feed it but it wont eat the food.I don't think it is because it does not eat that food because it use to eat very well. I am so scared that it might die. My mother tells me it is my fault because she thinks it got an infection of some sort since the bottom of it is a little red. I hadn't changed its water for like 2 days or 3 days because I was too busy with school work. She told me that ever since I did that it wont eat.Somebody PLEASE help me! I don't want my turtle to die ='[