Have you asked your Dr. or gyn if they could schedule a pelvic ultra sound for you just to make sure there's nothing else besides a cyst? I am not in any way trying to scare you, but things like ovarian cancer are hard to dectect, and women who have had it have all complained about changes in bowel habits (d/c switching back and forth), fullness in the abdomen, abdominal pain, pain in back, and leg pain. I myself had a pelvic ultra sound done two months ago, because I was experiencing all of these symptoms - it came back normal, but all of us women should always pay attention to anything going on "down there".
I really hope I didn't upset you by telling you that, but I think it is something every woman should know. Especially women with IBS, because things going on can easily be shrugged off to : "oh, it's just my IBS."
I wish the best for you CathyA,
P.S. here is a web site I have visited.