I'm a 51 one year old woman of average weight and size. Over the past few weeks, my abdoment has become extremely distended to the point where I can barely bend over to tie my shoes. I'm fatigued and have a general feeling of malaise. I have constant pain across the middle of my back and some breathing difficulty. When I bend over, I have pain in my lower abdomen. I do not have has or a UTI. My doctor says the distention is unexplained and is sending me for an xray and ultrasound. What could this be?