Low urine flow, pain on penis, low

I am having this problem for last 17 yrs.there is pain on circumference of penis, sometimes white substance,I also found my urine flow is also low.Due to pain my libido has also reduced drastically.sometimes also problem in erection.due to this pain sensation sometimes my erection finish during intercourse even without discharge n am not able to regain erection.Moreover after discharge I never get erection for next 24 hour.My tests for uroflowmetry n other were normal 10 yr back.someone was predicting that there is some obstacle in my urethra.please suggest what is the problem and solution.To whom should I consult-skin specialist,sexologist or urologist.pls also suggest good Dr in Delhi.How about b l kapoor or r g stone greater kailash.Name some good Dr.