Is my 7 month old kitten too young to be pregnant?

Yes, it is not impossible for a cat to become pregnant at five months old. Most kittens reach sexual maturity around six months old. Due to this, it is best to spay a kitten around this time, especially if she has her first season at such a young age, as she is just a kitten herself. It would be incredibly dangerous (and possibly fatal) for her and any unborn kittens if she were allowed to get pregnant.