Painful Spasm In Lower Right Side Of Abdomen After Holding

Painful spasm in lower right side of abdomen after holding urine. Have urgency, no UTI. Have had ultrasound, ct scan, & MRI. All inconclusive. Not kidney stone either. Will have urgency & frequency at times, but if I hold it too long, and almost feel like I squeeze so hard to not pee my pants, when I get to the bathroom the urine comes out forcefully, and not a lot, then within 5 mins. The severe cramping starts and just gets stronger. If I move & use stomach muscles, then it intensify but it's always on my right side diagonal from umbilicus. A heating pad helps it to subside after 1-2 hrs. Then left with internal residual soreness for 24 hrs.