Yeah you probably have an underlying issue that's making you so attracted to being high. Maybe you just love doing it. But it's almost certainly more than that.

"All in your head" means mentally addictive. Anything can become mentally addictive if it's a pleasurable activity. Physical addiction involves the body's actual reactions to not having the substance (and there can be mild withdrawal). You are mentally addicted to marijuana and once you find out why, you can work on that, the source of the problem, until you reach the point where good judgement in use and controlling yourself are easier and can be done if desired. The fact that you're aware of it and it bothers you shows it's an addiction. You can certainly get by being high all the time and day to day, but it's supposed to remain a conscious choice that could be turned down if you felt like it.