I Thought A Had An Ovarian Cyst That Was Causing

I thought a had an ovarian cyst that was causing me pain on my left side. When I went to the Gynecologist she did an internal sonogram that showed no cyst present. They then did an external stomach sonogram which did show something about 2 cm right above my left ovary. I have had a dull constant pain on my left side for over 3 weeks now....was wondering if it could be diverticulitis. I have a CAT SCAN scheduled for Wed. just wondering what else could cause a persistent dull ache. My urine test came back fine.