a cat needs to be pregnant for three weeks before you see the enlarged teats (known as "pinking-up")

So, hypothetically, if she got pregnant the day before you found her, (a little over a week ago) - the vet should know if she is pregnant in less than two weeks.

The cat could be eating so much because of worms or because she is finally getting a decent amount of food and has catching up to do. She's so young, she could just be storing up for her next growth spurt.

Are you feeding her kitten food or cat food? It's always best to go with a Vet's recommendation, but I switched my kittens over to cat food when they were 6 months old.