Fever, Cold, Persistent Headaches, Back Pain. Taking Ranitidine. History Of Gastritis. Treatment?

my father is suffering from fever and cold with pursuant headache . he is 58 years old and currently serves in a bank which requires daily sitting around 5-6 hours and that is the reason he to have back pain due to gastric. he weighs 75 kg . he is currently taking Acilock ( ranitidine ) on a regular basis ..please advice what should we do get him rid of frequent health problems. if you need any other information do let me know. thank u.