Flossing should not be painful with normal, healthy gums. You may feel discomfort when you first start flossing, but don't give up. That discomfort should ease within a week or two. If your pain persists, talk to your dentist or dental hygienist. If there is discomfort and bleeding you may have gingivitis or periodontal disease. See your dentist if you think you may have either of these dental diseases.