An ovarian mass is a very common occurrence in women and can indicate a variety of conditions. However, if this mass is causing you so much pain that the prescribed pain medication is not controlling it, and it is impacting your bowel movements and causing you nausea and affecting your ability to eat, I would recommend returning to the emergency department and not waiting for your scheduled appointment. If you are able to get in touch with your gynecologist, call him or her and ask whether you should return to the emergency department immediately. However, if you are not able to reach him or her, return to the hospital for pain management and further evaluation.
In terms of what this mass could be, there are a number of benign (not cancerous) conditions that may explain this finding. An ovarian cyst is a common finding and is generally not dangerous, although there is a risk of cyst rupture. This could present as a "complex mass." A teratoma is another benign condition that may appear complex because it is composed of different tissue types. Complex just means that there are different components to the mass that make it look like there are different sections within it, rather than one homogeneous collection. A fibroma would look more like a "simple mass" rather than a "complex mass," for example. Of course, the most concerning condition that this could be is a malignant (cancerous) ovarian mass. As mentioned above, there are a number of less serious conditions that this could be, so I would not become overly worried at this point, but it will be important to see your doctor
to follow up on this and perform testing that will determine what exactly this mass could be.
For now, however, I would recommend calling your doctor, and if you cannot reach him or her, returning to the emergency department for pain control and an expedited evaluation of this mass.