My fish is really fat and has red spots around his/her belly. Any clues?

My Danio fish, Danny, is really fat and has red spots around his/her belly. I first noticed the spots last night (Oct 16). We think (s)he's pregnant, but we're not sure. I first noticed the big stomach last night, too, but I'm not sure how long (s)he's been like that. We have only one other fish in the tank who we're pretty sure is male. It's some kind of shark and his name is Bruce Lee. He's black with a red tail and fins.