I have a mitrofanoff urinary diversion and my urethra was stiched up during op, i am getting leaking through my urethra, don't know why, ?

Urethra still patent: Unfortunately closing off urethra or bladder neck is both difficult & has a high failure rate. Virtually impossible to do from below & best performed suprapubically by open surgery from above. Bladder neck has to be inverted & closed in 2 layers. Possibly your urologist could inject coaptite around bladder neck cystoscopically via the mitrofanoff channel using a pediatric cystoscope.