You are driving a stepper motor, that means you need to generate a sequence of signals into its windings to create steps. Lets say that 1 hole revolution has 360 steps, you will have to generate 360 signals so that the stepper rotates 1 turn. When you try to apply this signals to fast the motor will miss some steps, and if it is too fast it will only jerk a little bit.
Try slowing down the signal generation. Normally stepper motors need a ramp to accelerate, by that I mean that the aceleration of the motor shouldn't be from 0 to full speed, but accelerate progressively until reaching full speed or the speed needed.
How is your program and what connections did you make?
Ivancho