your fish is not pregnant ... what have you fed this fish with - ? is it clean or have you over fed them . The best feeding frequency is only maximum 2 times per day.you may have to make it vomit out what it have swallow in. it may not make it but if you want you can try.

This is probably a digestive problem, don't feed your fish for a couple of days. Then on the third day feed your fish green peas, fresh or frozen, just make sure that they're soft enough and cut the peas into small enough pieces for your fish to eat. If you have a fish that has trouble swimming I would try to incorporate green peas into the fishes daily diet. Don't feed your fish flake food, flakes tend to make goldfish have digestive problems. What kind of fish do you have anyways, it almost looks like a pearl scale.......maybe it's just the belly. Where are all the educated people on this forum? Seriously?

It's swim bladder disease