Your block is great along with your choice of fabric. Did you slow your speed down? This helps a great deal in getting a straight sewing line. If your machine doesn't havew the option of slowing the motor you may have a hard time controling the machine speed. To help slow it down you can wedge a small sponge under the foot pedal and you be surprised how much control you gain.
Love your block. Keep up the great work and post pictures as you go!
peace