How can I tel if my cockatiel has a binded egg in her?

She is 8 and half months. I got her from a woman wher she was being abused in a cage with other birds. Shepassed 4 eggs 2 weeks ago and it seems like for 9 days now she has been panting like she is going to pass another egg. She spreasds her wings out at bottom of cage and she does sit on teh eggs she layed. Not sure if they are fertile so I am waiting 25 days to see before I dispose of them. She acts normal at times and wants out of her cage to love me and walk around. Her poop is different some large that look like creamed spinich and some small that look normal. She is eating fine but seems to be uncomfortable at times. I am worried about her and want her to be okay. She is just a baby and I have never had a female cockatiel before only males. Can someone help me? Thank you