The key to consistency is consistent form. Ideally, you would attend a shooting clinic or have someone who knows good form coach you. I see you're from Australia, and I don't know how available those things would be down there. But if you can post a video on this forum, folks can give you some advice. If you have never been coached, it is likely that something in your form is not up to par; probably something you are unaware of.
You didn't mention how long you have been at this game. Like any sport, we have our Tiger Woodses and our All-thumbs, but for the majority of us it takes several years of regular practice, meaning several times a week at least, before we can begin to tighten up our groups with any regularity.