Give yourself some credit. You are struggling. Don't underestimate what you are dealing with and how you're feeling. I think others can speak to this as well, but I know that no one ever noticed when I was hurting myself. No one knew unless I told them. I cut for almost 4 years before my parents found out and even then, they only knew after reading my text messages. I pretended to get better so they would stop acting so odd around me and treating me poorly. And even after that, I continued to cut for another 6 years and they still don't know.
You need to open up to someone you trust. Let someone help you. If you don't think you can do it on your own, please let someone help you.