Well I don't know if you're home and able to get her in right away, but if not, you will probably want to get her to the closest Avian vet to you ASAP, as it sounds either like classic Egg-Binding, or even more probably since you said this has been months is an already rupture egg inside of her shell-gland/uterus, as when the eggs rupture inside of them then you've got a whole other set of signs/symptoms/issues that take longer to appear, sometimes quite a while, as it then presents like an illness/infection...
Signs of excessive lethargy/sleeping, not eating much or at all, being fluffed-up a lot, having them picking around their vent or belly, etc. are signs of an infection...Something isn't right, and having lost a breeder to Egg-Binding once myself (even though I treated her immediately at home on the first signs and then took her to the 24/7 animal hospital where my CAV is on-staff, and she still died the next day) i don't want your baby to go through that, nor you, as it's so horribly painful for them. And it's horrible to have to watch as well...
Just an FYI to you, if she goes into breeding-season often and has a history of laying infertile eggs, please do be sure to get her a bunch of extra Calcium in her diet every single day, whether she's in-season or not at the time...The most-common cause of Egg-Binding/Ruptured Eggs is them not getting enough Calcium to properly form the shells...I don't know what her regular, daily diet is, but she needs to be on a fortified pellet staple, with a healthy, fortified, varied seed-mix without sunflower seeds in it as a supplement to the pellets, then lots and lots of fresh veggies every single day, with fruit as well...And getting her either a large Mineral-Block/Treat to have at all times to chew-on/eat will help to provide her some extra Calcium (keeps their beaks busy too), along with either cooking her some eggs with the shells ground-up and mixed-in every day, or just simply buying a bag of commercial Egg-Food to add to her pellets/seeds (any Petco sells Egg-Food in bags) is a really good way to get the calcium that she needs so that this won't continue to happen...
I hope your vet is a Certified Avian Vet with much experience in breeding/laying females...A plain-film x-ray and some blood work is a really good idea to see what is going on and to get her baseline levels...Keep a close eye on her until you get her to an Avian Vet, any whining/crying, heavy breathing/panting, sudden picking at her belly/vent, vomiting, etc. is an emergency...and check back here if you have any other questions...