Hi I Would suggest you to go for blood tests and ct scan chest in case corona testing is not available. Decongestants alone will give temporary relief,  so i would suggest spray

Hi , you have explained the treatment history very well , so it becomes easier for me to narrow down and help you how to proceed further . Let me tell me that your doc has treated you with antibiotics and anti allergy medicines and you getting symptomatically better is a good sign. Further more , we have to check his routine blood counts . On basis of reports , we can suggest whether it’s infective or allergic in nature . I’d report comes to be normal , then a nasal endoscopy should be performed to look for any nasal mass or any other pathology which can be related to it . Finding the cause is required in this case , before proceeding with the treatment .