Is pain in the gums when brushing usually a sign of periodontitis?

Not necessarily: Aggressive brushing with hard bristles may cause pain in the gums. Bleeding with routine brushing is a more common sign of periodontal disease. You should be seeing your dentist at least once a year for preventive care and should the issue with her/him. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Not always: Periodontal disease often has no outward signs... that's why patients don't always know they have a problem. Have your dentist evaluate your periodontal health.