My fish double it's size but on it's stomach but I think it's dying because it's just floating around isit normal because its giving birth or is it dying. sry no pics. And if it's pregnant when will it give birth I just saw it like this right now.

Hahaha fish lay eggs silly.

Ignore that persons previous answer. Yes fish do become pregnant. Depedending on what species of fish it is, if it is a sword tail, molly, gupy, or platy, all species of livebearers. yes it could be pregnant. also fish do change size when carrying eggs inside of them. Depending on what species it is will tell you what the problem is. Here is my email. Respond with species of fish and how many of the same species are in the tank.
Goldenarcher1328@yahoo.com

pets question and answers,www.5d2d.com

Thanks and i'll try to give you as much help as i can. currently i have two pregnant fish. one molly and one cory cat.

if it is a live bearer, like previously mentioned, guppy, molly, endler, sword tail or platy, it is possible a fry has gotten stuck in the birth canal, if the fish is actually pregnant. If this has happened there will be more fry growing inside that will keep growing and not be able to get out as they will then be to big. This has happened to my cousin a couple times mostly with guppies, but it does happen with all live bearers.
If it is not a pregnant live bearer, there are some diseases and disorders that can mimic the look of pregnancy. I don't have any experience with them myself, but the name of fish you have would definitely be helpful in determining the possible problem.