I have a really big guppy. I think she is pregnant but I'm not sure. She has been big for about three weeks and I just want to be sure she's not sick or anything.
Yeah, I had a guppy give birth very recently and she looked exactly like that. Prepare yourself, you can get dozens of fry: mine only gave birth to 12, but this is the low end of the spectrum.
looking at the picture anyday now. Your tank doesn't have enough vegitation to keep the young ones safe. I would get a breeding set up NOW if you won't to keep them. If you cant do this then get something to put her in and add lots of plants in there.
Agree with desertgoldhound.... she's preggers, and get extra coverage for the fry. I used anachris as top floating plants or you can isolate them in the tank w/ a hang on fish net breeder.