Painfull & frequent urination. Me sir!

I found the symptoms bellow- *painfull and frequent ,urgent, drop drop urination occuring since 6-7 months *burning & itching sensation at urethra as well as inflamation in bladder and lower abdomen *feel some blockage of urine in penis during urination and taking 1-2 min time to initiate urination * not emptying the bladder completely *sometimes penis get compressed before initiate urination if i hold and delay the urine for some time *since some days feeling weak thigh and fatigue in thigh and knee with whole muscles in both leg's and discomfort in standing i have already tested (like ultrasound, sonography ,urine culture, blood test etc.) and not found any abnormality in kidney, stone problem, prostate gland, or any infection ,nothing found, not a UTI docter said normal pain still i have the above said symptoms. but i guess, it may be a urethritis problem to which my symptoms are matched found in internet, but i am confused how to cure,plz help me sir