Can an irritation on the urethral opening that causes symptoms such as weak urine flow & incomplete bladder emptying last 2 weeks and longer? i've been told my symptoms could be due to irritation but is it normal for irritation to last this long?

Not urethral: In my opinion your symptoms are more characteristic of bladder outlet obstruction or a neurogenic bladder disorder. Urethral irritation usually causes urinary frequency in small amounts often along with burning or other discomfort during urination. A urologist is best to evaluate you and order appropriate testing. If you've already seen one, get a second opinion from another urologist.