Hi and welcome to the forum! I am glad that I can help you.
You would like to know the cause of the symptoms that you experience.
Ovarian cancers may appear on one or on both ovaries. If the case is operative, surgeons perform a total hysterectomy (ovaries, fallopian tubes and uterus are removed). If there are no positive pelvic lymph nodes, patients are treated with radiation. If positive lymph nodes are found chemotheraphy is required. Side effects of both radiation and chemo are dermatitis and radiation burns, gastroenterocolitis (presented with diarrhea), thrombocytopenia, anemia, etc. Rarely, in the case of spreading of a malignant tumor in the nearest organs such as the rectum, patients may experience difficulties with passing the stool. Sometimes individuals develop diarrhea after experiencing constipation, which in certain cases may be considered normal.
Given the data that you described, it seems likely that you may be experiencing the constipation due to eating habits. Avoid chocolate and bananas to avoid constipation. Consume liquid-like meals to improve bowel movement. In case you experience diarrhea that is non-infective, you may consider eating one or two bananas a day, usually one day, until the diarrhea stops.
Please keep in mind that I provide medical information only. I am not able to diagnose medical conditions online. Please contact your doctor for further advice and information about diagnosis and treatment options.