Maybe that is it.
I do feed her a fairly high priced cat food. It is made with all natural products- no byproducts or fillers. Although it isn't from a vet. That may be why she doesn't eat or go to the bathroom as much. I think that she is healthy. She has always been a tiny cat, when people see her they think that she is a 6 month old kitten. She is short and skinny for her age as was her mom. I am hoping that it is just the way she is. Also she hasn't been fixed yet so she is very active ( she loves to chase our bunny!). Maybe she will put on more weight once she gets fixed.
Thanks for your thoughts