Pain right lung and back with slight dry cough for 2 months. had bloods & x-ray. all fine. docs not too concerned. i am extremely worried lung cancer?

Very low probability: It could be reflux or allergies, perhaps even asthma but not lung cancer at your age. Good luck. +.

Further evaluation: If you are a smoker further evaluation with a ct scan of the chest may be indicated; you should also consider asking your physician for referral to a pulmonary specialist for evaluation of the persistent cough. On a good note- cancer is progressive so the longer the symptoms remain stable the less likely cancer is the cause.