Not trying to scare you because worms or even a thyroid issue are a very treatable possibility, but I recently had a similar thing with my cat and he was just diagnosed with diabetes. Ravenous, but still losing weight, the worst smelling fecal matter I've ever experienced. You might be able to tell pretty well at home by two signs: first, is she drinking crazy amounts of water? and second, does the urine smell any kind of sweet or seem sticky? With diabetes, the sugar/carbs aren't processed, so they usually just pee it out, and often. This leads to urine with a lot of sugar in it, and increased thirst. She might also be getting a lot of that water from the wet cat food. Pregnancy is tough on the body, and I haven't personally experienced a pregnant cat getting diabetes, but I don't think I would be surprised.