Diminished urge to defacate

I am a 55 year old white female with a history of diabetes (1980) and a kidney transplant in 1999.  I have had a colonoscopy which was negative.  My problem is (and my doctor cannot help me) is that my urge to have bowel movements is diminished.  I feel like I have to go, but when I do, I have to push to have a movement and I always feel that I have not eliminated all of it.  I am not constpated because my bowel movements are fully formed and are not hard or like little hard balls.  I am at my wits end in trying to find a solution to my problem.  Any thoughts.