I had the same problem when I learned to play guitar... I could play absolutly anything with just 3 fingers because I have long and skinny fingers. However, when I got more into theory and technique I wanted to learn how to do it the right way... I did want most people do. I got a scale book and ran through scales up and dow, back and forth until I could play just as well with all four fingers. It helped me learn scales, helped with overall speed, and it helped with dexterity. Just have to committ yourself to it and practice.