Exactly what Merry said...a picture, or the instructions for the part of the pattern you are having trouble with would be very helpful in figuring out the problem.
Is the project worked in the round or back and forth? What stitch are you using? It could be that your hook is too big or too small and you need to adjust that to get the right tension. You may be missing the last stitch on each row or picking up extra stitches along the way. So many things could be causing the problem, so the more information you can provide, the easier it will be for us to help you through it...which we will!
Don't give up!