Other possibilities are irritable bowel syndrome, hepatitis(inflammation of the liver),
kidney stones, pneumonia, musculoskeletal pain, lower rib fracture and malignancy. Irritation of the nerves supplying this area can also cause pain. Irritation can be due to nerve compression or pinching due to any spine related pathology.
In females,ovarian pathology can cause such symptoms. You should get an ultrasound right upper abdominal area done to confirm the diagnosis.