Welcome! I see it's your first post. I'm one of the teaching staff at GTO.

Your problem is swing path. You are pulling the ball, which means an out-to-in swing path with a club face that is square to the new swing path.
To fix it is quite easy, actually. There are a number of drills to use, but I'd like you to start with this one because the pull is quite 'small' and you need to do is redirect the club inside a little:

1. Setup to the ball and check your fundementals. Next, without moving your torso, pull your right foot back until your toes are level with your left heel. You should have a quite substantial closed stance.
2. Now hit golf balls practicing like this, focusing on bringing the club back on "the line" (swing path) that is parallel to your toes.
3. Don't throw the club at the top, don't let your shoulders turn left pulling the club outside-to-in - let it drop natually as you drop your right elbow into the right hip.

Try it ... if it doesn't work there are a few other drills to try. I like this one becuase it is very quickly and easily gives your the feeling of the correct 'in-square-in' swing path you're looking for.

Focus really hard on not letting the shoulders dominate the swing.

__________________
Golf is easy ... once you know how.
Graham Arnott, teaching professional
Kelrosa Golf Studios
www.kelrosagolf.com
Class 'A' PGA Member
Full Member: World Golf Teachers Federation (GB&I)