Yes you can have both therapies at the same time, and yes you can get better. If by "severely mentally ill" you mean emetophobic, this is a phobia... an exaggerated fear... an anxiety disorder... and emotional disorder... not a mental illness. We lump everything into two categories: body or mind, and if it's in your mind then it's assumed it's a mental illness. But true mental illness is something that causes you be out of touch with reality all the time, doesn't get better, and always needs to be medicated to be controlled. That doesn't happen with emetophobia. Your thinking is unrealistic about vomiting, but you yourself aren't living in a little world of your own. So please, drop the "I'm mentally ill" label and that will be the first step to recovery.