5lb, 21 month old female - normal?

hi,

my cat keylah has always been small, she was a tiny kitten, and now she's a small cat. however i'm starting to get slightly worried. she's 21 months old and she's only 5lb, no matter what I feed her, she doesn't seem to gain much, and she doesn't seem to like many of the foods I give her, sometimes she'll just refuse to eat. She's always been a tempermental cat except with me, but everytime I pick her up, she'll cry when I go to pick her up, although she's okay once she's been picked up. Her kittens Malik & Jerryn are 7 months old, and although not exactly the same type of cat Keylah is, obviously since they've got a lot of their fathers genetics in them, they weigh 6.6lb each and are growing fast, they also have a huge appetite. she's was de-sexed recently, so perhaps the temperment is from that, and I wormed her today, If she doesn't get better I'm taking her to the vet, but is 5lb severely underweight for a 21 month old female norweigan (domestic) forest cat? does it sound like she may have something wrong other than being a picky eater, a tempermental kitty and just "small" in her genetic structure?

thanks

Autumn

I was going to say that some cats are just small, but Norwegian Forest Cats are supposed to be big cats, like Maine Coons. I would definitely take her in to make sure that nothing is going on that is preventing her from eating. What types of foods have you tried (canned or dry)? It is possible for cats to be genetically small (my boyfriend has one who only weighs about 5 pounds and she is 6 years old), but with your kitty's breed I would get her checked.

Also, the vet may have safer and more effective dewormers, so I would be inclined to get one from him/her rather than use an over-the-counter product.