Just like everyone else says on this thread, just give it time and you will eventually be able to find the boundary more frequently. Don't try to force it and swing from the hip to try get the boundaries, as this can lead to you being very bottom handed in your batting, just bat like you do and sensibly. Practice shots while facing a mirror and make sure that you really bring that top arm up while driving, and perhaps even practice against throw downs using only top hand. This will strengthen your top hand and help you play through the line better. Watch your shapes as you do this and remember to keep a good balance before, during and after the shot. Once you grow a little taller and start using short handles, you will find that you can hit the ball further.
Hope this helps!