Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. To get right to your question, the answer is yes, it could be pneumonia (pneumococcal or other). 16 days is too long for a common infection. The two phases may indicate a complication (like development of pneumonia during the course of milder respiratory tract infections) or a new infection. The only way to find out is by testing. Your doctor may identify signs of pneumonia or other infection with clinical examination. Streptococcus pneumonia can be detected with a simple urine test (antigen identification in a urine sample). Other tests that may prove to be useful include a complete blood count (to check the white blood cells count and differential), C-reactive protein (high values may indicate a bacterial infection, lower counts are more in favor of viral infections) and a basic biochemical panel. In case of doubt a chest x-ray would clear things up. A negative X-ray at this point would exclude pneumonia. So in conclusion, I believe that this infection has lasted for too long and you should be examined by your doctor as soon as possible to diagnose the type of infection and suggest appropriate treatment. Hope I have answered your query. Let me know if I can assist you further.