Thank you for getting back to me. It is possible your fish is retaining eggs, but the fact that she is upside down also makes me suspect swim bladder disorder. She could even be suffering from both conditions. Swim bladder disorder can be caused by constipation, which also leads to a bloated belly. Something that may help the fish regardless of what is wrong is to feed her nothing but thawed out and peeled peas for a few days. If the peas are too big, you can smash them. You may need to hold them right in front of her mouth.
You are on the right track with the baths. The goal with baths is to have the fish lay the eggs or reabsorb them. Epsom salts are the only thing that has been found to help with that. Most goldfish keepers use 1 tablespoon of Epsom salts per gallon of water, so you may want to try this higher amount. Leave the fish in the bath for 15 minutes each day. I wouldn't add any Epsom salts to the tank. Instead use Maracyn according to the package directions to prevent infection from any retained eggs. The Epsom salt baths, Maracyn in the main tank, and feeding peas will be the only measures you can take. If the fish is suffering from swim bladder disorder, the Epsom salts won't help.
You'll also want to reduce the ammonia and nitrite levels in the tank. I realize that some test kits say there are safe amounts of these chemicals, but when dealing with goldfish, the only safe amount is none. These chemicals can be a factor in almost any health condition.Start with a 25% water change, being sure to replace it with dechlorinated water at the same temperature as what is in the tank. Tomorrow, test it again. If you still have ammonia and nitrites, change another 10% of the water. Do this every day until the zero level is reached. If you can't get to zero, it may be that your fish have outgrown their tank. It used to be recommended to have one gallon (about 4 liters) of water per inch of fish. that still holds true for tropical fish, but not for goldfish. There are various recommendations, ranging from 2 gallons (8 liters) per inch of fish to 30 gallons (about 113 liters) per fish, regardless of size. Another recommendation is 1 square foot of surface area per inch of fish. So, you see there is no hard and fast rule. I’ll share my own experience with 12 inches total of goldfish (3 fish). They are in a 90 gallon tank. I have an undergravel filter, a hanging filter, and a powerful canister filter. It takes all three of those filters to maintain perfect water quality. Regardless of tank size, frequent water testing is needed.
If you want to do everything possible for your female, you could consult an aquatic vet. The vet could determine with certainty what is wrong and prescribe a proper treatment. If you want to do that, this link will take you to a directory of vets:http://www.aquavetmed.info/index.cfm?PID=6
If you have more questions, let me know by clicking on REPLY. I hope your fish will be fine.
(The above answer is intended for informational purposes only. If your pet is ill, you should consult a veterinarian. )