I really just don't feel good. Am i depressed?

I don't know if this is the question that i should be asking a doctor but i need help. I am so afraid to face anything in life. I'm a teacher and have only been teaching for a short period of time but i think about teaching and its outcomes every second of the day. The holidays are over now and i'm back to school and i just have this horrible feeling inside. It may sound stupid but i am never happy when i think about teaching. I don't know if it is teaching that i hate or is it that i just don't feel that i am good enough in anything i do. as my parents say i have the qualifications but sometimes i feel that i overthink everything. any advice would be appreciated. I really just don't feel good right now about myself or my teaching ability.