Hello and welcome to HCM, Stomach ache can occur due to number of conditions. Indigestion is one of the common cause of stomach ache. Other causes include gastritis, infection etc. However, a clinical assessment is required to know the exact location of the pain. Since, there are various organs in the abdomen, the location of pain can exactly tell the appropriate organs responsible for the pain. An ultrasound may be required following clinical assessment. As you have mentioned you cannot stand too much since this position causes pain; thus implying that the pain is postural. Postural pain is known to occur in pain arising from pancreas, however, a clinical assessment and relevant investigations are required to know the cause and thus plan management. Thanks and take care Dr Shailja Puri