You are certainly right that hysterectomy is a major cause of prolapse. The uterus is the hub of the wheel of pelvic organ support and its removal causes great instability to the pelvic interior. Ask your doctor about the failure rates of subsequent surgeries for post-hysterectomy prolapse - I think you might find they are fraught with significant risk.
You may find that changing your posture to hold your bladder and intestines forward and away from your pelvic outlet is enough to affect your symptoms and avoid further surgery. Prolapse is extremely common and women the world over are learning to live well with these conditions by returning to natural female posture. The problems become more complicated after hysterectomy, but it might still be worth your while to see what others are saying about natural pelvic organ support at Whole Woman. :) Moonspinner.