hi thanks for your query at hcm as you said that you have pain on upper left side gum it looks like you must be having the tooth infection and the pain is referred to eye and cheek bone.. you have not mentioned about your age??? as if there is erupting or impacted 3rd molar it can also cause similar symptoms.. upper teeth are in vicinity to maxillary sinus so there is possibility of spread of infection to sinus present with pain on bending.. i would suggest you to go for a thorough checkup by your dentist.. get treated if any infection present by antibiotics.. go for x-ray if needed.. do warm saline gargles and oral rinses.. hope my advice will help you dr Priyanka