Codependency means you rely on a person. This can be because of illness (physical or mental), and in fact usually is. Have you been diagnosed with anything else (anxiety, depression, PTSD, etc)? If so, maybe he means your illness makes you codependent on her. It's not uncommon for people with mental illness to be codependent. It doesn't necessarily mean they feel like they can't survive otherwise, though. It basically just means they struggle to (as in have a hard time finding a job because of their symptoms, have a hard time shopping because of symptoms, etc).

Whereas with dependent personality disorder we feel we literally can't survive without the person whom we depend on. With us, there is often a deep seated fear of losing this person. Many of us may jump from relationship to relationship to avoid having to be independent. Being independent feels like an impossible task. I often fear losing my partner, because I'm terrified that I won't be able to support myself. I am not only codependent on him, but I feel like I literally need him.

Make sense?