Not sure what is wrong
Welcome to BYC. I would put on a rubber glove and stick your middle finger into her vent an inch or so, to check for a stuck egg. She may be laying internally or have salpingitis if you feel no egg, but that is only a guess. You may want to do some reading about those subjects, which you can do by entering the word in the search box at the top of the page or by Googling it.
Another thought is she could have a blockage in her gizzard. Let us know how she is getting along.
Edited by Eggcessive - 2/17/16 at 5:06pm