Appropriate Treatment

Hi, and thanks in advance for your advice, help and information.  I am a 35 year old who presented with mid-cycle light bleeding while on the pill.  I attributed this to having missed 2 pills early in a pack in 1/04.  Vaginal Ultrasound in 2/04 showed a lime-sized cyst on left ovary, which appeared "simple" and was thought to be functional.  Follow up ultrasounds in 3/04 and 4/04 showed some shrinkage, but no rapid resolution consistent with a functional cyst.  My GYN asked if there was a history of Ovarian Cancer in the family (there is not), and ran a CA 125 that came back "normal".  Suggested course of treatment is another ultrasound in 7/04.  I was put on a higher dosage OCP early on, and the bleeding has stopped, but I have intermittent pain and have to run to the bathroom far more often than normal.  I also have been eating like a horse, and fail to gain weight, which is unusual.  How likely is ovarian cancer to appear as a simple cyst on ultrasound?  I am scared to death, and wonder if maybe a more aggressive course might not be advisable?  Thanks for your help - I want to be as informed as possible!