Improper urination from past 4-5 years.

Iam Abid Raza , Iam suffering from urinary problems from 4-5 years. I consulted to 4 doctors and many tests/scans but no result. Actually I can't urinate properly, I don't feel that my bladder is empty, after urination I feel that some drops of urine are still there in my penis and on any sudden motion(such as sneezing) I feel that its coming out and feel some sensation in my penis. This is the reason I use to sit on toilet for very long time untill I get satisfied but still problem remains as it is. Due to sitting ontoilet for very long time everyday ( approximately 40-60 minutes just to feel that my bladder and penis are empty) my legs are now being curved at knee and my joint is now displaced and I feel pain sometimes, from past 2-3 months I feel itching around my penis and I noticed that the skin around the pennis are dry and white. I also can't pass stool regularlyand Feel pain in my motion passage also. (I want to add that I am very weak and skinny guy of age 18) Thank you