Do higher amount of gas for a month & stomach pain around belly button for a week (gets relieved after motion) indicate stomach ulcer or liver tumor ?

Neither: Try to alter your diet to see if that brings relief. If that does not help, you should consult a doctor for the stomach pain as that may be due H pylori infection. 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. 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.