I used to have the same thing. I don't recommend going deep into sports psychology (with a fixed timeframe for improving) because it can do more harm than good.
But a couple of things that helped me:
- A couple of warm-up racks just spreading out the 15 balls for easy, fairly short shots around the table (with no clusters) is a nice warm-up that gets your rhythm going
- I don't know whether you're currently playing every day, but if not then when you do (e.g., in the run-up to your tournament), it can give you a momentum that carries over day-to-day. (For me, the effect really hits from the fourth day of playing, and I find it best to have shorter sessions each day so I still feel fresh)
Both of these things, for me, provide some of the momentum and confidence that seems to come with a couple of drinks. You've got time to experiment with them if you want to.
Another thing that helps me is, when shooting, to focus on the rhythm of my swing (including warm-up strokes).
But overall, the objective is to relax and play, not to over-think it.