Bad habit or Mental Disorder

I'm new to the forum and I've been picking for 2 years but didn't realize I was causing the lesions on my body. I was diagnosed in early February 2018.

I've been told that I have a bad habit. I'm not sure I believe that. I think it's a mental disorder. My doctor says this is a temporary thing. I don't believe that.

Can anyone help me understand?
Elaine