When i eat something,after 1-3 minutes i feel a sharp pain on my upper stomach. when i searched through the web, it shows either indigestion or ulcer. the pain goes on and off even if i don't eat anything. what should i do, do i need to see a doctor?

Yes, it could be. You can make a therapeutic diagnosis by taking antacid liquid OTC such as mylanta about 30 minutes before meals and at bed time. If pain goes away after 3 days, you probably have either condition. Then you can start famotidine or pepcid AC (OTC), 20 mg twice a day for 2 months, avoid spicy & alcohol. If pain recurs with or without med, see your doctor for ruling our H. pylori.