I'm sad all the time and a big loss of appetite and thoughts of self-harm is this depression or something else? :(

It sounds like you may be experiencing symptoms of depression. It's important to talk to a mental health professional or your doctor about how you're feeling to get a proper diagnosis and receive help and support. Self-harm is a serious sign that you are struggling and need help. Please reach out to a therapist, counselor, or crisis hotline for support. Remember that you are not alone and help is available.