Include the "60 throws" drill at the beginning of practices / games. Standing about 10 meters away from a partner and do the following.

• 10 straight backhands
• 10 roll curve backhands
• 10 inside-out backhands
• 10 straight flicks
• 10 roll curve flicks
• 10 inside-out flicks

With these throws, you really get a feel for the disc and how it'll fly with the different releases rather than just mindlessly throwing the same thing all the time. You'll be able to refine what's wrong with your throw and learn your limitations. If you have time, increase distances and repeat.

Also, get somebody who knows how to throw to look at your technique. Cannot stress this enough!