Hi there.. chest pain could be due to many reasons like chest muscle strain, esophagitis, esophageal spasm, gerd, gastritis.. or since you have fever associated , it could infection of lung like lrti, tb, lung abscess , pleural effusion.. it's not lung cancer, your too young for it and just 4months of smoking isn't enough to cause cancer... symptoms of many diseases over lap so please don't worry thinking negative.. quit smoking, get sputum examination and ecg done once.. if needed get endoscopy also done once.. consult nearby chest physician..