puzzling problem

Hi. I am 55 and went to see my gyno. in Jan for my yearly. She was concerned I had a light period at my age and ordered an ultrasound which led to an MRI. She told me my uterus lining is fine but I have a coil of fluid behind my uterus which is unexplained. It is causing me some discomfort when I have a bowel movement and sometimes when my husband and I have intercourse. I was sent to a GI doc and he had me do bloodwork, which showed a slightly high level of inflammation but everything else was normal. Also had a colinoscopy and he ruled out cancer, crohns, diverticulitis. Lots has been ruled out but no answers as to why it is there. Has anyone else out there had a problem like this?