Is my dog pregnant, or in heat?

I have a rat terrier/shitzu mix dog who is about 6 and 1/2 months old. We also have a big australian shepard mix boy dog that hasn't been fixed cuz of the price it would be and he is about 13 years old. And he has tried everything in the book to get to her. And the girl, (bailey) is bleeding in the area where she pees. And she is really, really moody and pissy. Plus, her are twice the size they were last month. And she's gained 5 pounds since last week. Is she pregnant or in heat?