How many stitches did you begin with? For example, if you started with 9 stitches, you would knit one, then yarn over. Because the instructions are in brackets, you knit one, then yarn over, then knit another one and yarn over. (so in answer to your question, you need to yarn over after every stitch you knit) If you began with 9, then you should end up with 18 stitches at the end of the second row. On round four, instead of just knitting one stitch, put your needle through 2 stitches and knit it like one, then yarn over again. Your yarn overs are adding stitches and your knit 2 together are decreasing. If you are short stitches, it is likely that you missed a yarn over. Is this the beginning of the pattern? If it is, I would recommend starting over, and just count very carefully.