Hello You didn t mention about the sexual relation history in recent past , this is very important . If you have sex within one year with an unknown person then please get in blood for H IV ( because diarrhea, nausea or vomiting, general weakness, burning sensation , generalized body ache are all an indication of HIV infection , if contact history is there). The next reason of such symptoms may be due to peripheral neuropathy ( reason may be diabetes or deficiency of B12 ) . So for this consult a physician and get his opinion. As you mentioned that there is discharge from penis , so this discharge in young ( 17 -18 years ) may be due to semen , phosphaturia or pus . Get in swab examination for this discharge . As your history of illness is very ambiguous so very difficult to estimate the diagnosis . In my opinion consult a physician and get his opinion as physical as well as clinical examination is very important in such type of cases. Good luck.