Discipline is not punishment and hurting children physically should NEVER be a part of discipline. I believe this is a significant enough problem to warrant at least some short-term therapy with someone who has treated adults who were abused as kids. Interview therapists as to their experience in this realm and then select the one you feel most comfortable with. If this is not dealt with you will also begin to doubt your overall abilities to parent. Reading about successful ways to discipline with love and respect for children will complement your therapy. A few good sources to begin with are : Discipline with Love, by Stephanie Marston, M.F.C.C.( an audiotape) and the book, Discipline without Shouting or Spanking, by Jerry Wyckoff, Ph.D. If you can't find these in a bookstore, they are available from Glazenbrook and Associates, P.O. Box 138299,Chicago, IL 60613.
It's time you freed yourself from something that was done to you when you could not defend yourself. I am sure you will be a wonderful loving parent who learns to discipline with love, humor and creativity. I wish you good fortune on your brave journey.