My Wife Had A Ultra Sound Yesterday And It Showed

my wife had a ultra sound yesterday and it showed nothing there. she has been suffering with terrible pain mainly when she goes to bed or lies down for several weeks. she had a fatty tumor removed about a year ago and we thought it might be another one or being she said it feels like it is inside her we thought of cancer but thank god the ultra sound showed no masses or anything. what could be causing her this pain and what can I do to help her so she can sleep at night. please help