Is my mom TOO overprotective? Help?

I am 14 and almost a sophomore in high school. The other day I told my mom I was going for a walk and she flipped out. She told me it was dangerous for me to be all alone. My neighborhood is in a safe place, I walk to my bus stop almost everyday with my brother. I am very small though. But I have depression and walking outside (with my camera for photography) alone gives me time to think and I feel happier after! She doesn't know about my depression though, and I'd prefer not to tell anyone. I am kind of a loner so... I can't even sneak out and tell her I'm with someone. Help? :[