It sounds to me like you are experiencing depression. The feelings of worthlessness seem to be a constant symptom of depression. If you read the posts on this forum you will see the same sadness. You are not alone. If you can read some of the posts here and read some of the information at the top of the forum. Sometimes if you can see your symptoms as part of a disease it can give you a little distance help you stop feeling shame and guilt. These bad feelings are not the truth. They are only symptoms, like fever in a flu.
It's a good idea to see you school counselor or dr. You will need help to overcome your depression. Almost everyone does.
Online user gave some good advice also.
Here you will find people to listen to you and if you like you can join social groups and enjoy interacting with the kind people here.
Post whenever you feel like it. We are here to listen.