Try replacing the bolded values to 0f
Code:
pPosition.X += MathHelper.Min(GamePad.GetState(PlayerIndex.One).ThumbSticks.Left.X * 3.0f, 3.0f);
if (!gameStarted)
bPosition.X += MathHelper.Min(GamePad.GetState(PlayerIndex.One).ThumbSticks.Left.X * 3.0f, 3.0f);