My cat has just had her third litter and has only had one kitten I didn't see it being born and there was no signs of blood or the after birth is this normal or could she be having more it was born roughly5 hours ago thank you

It's not abnormal for a cat to have only one kitten, but it is possible there will be more.

You need to get your cat fixed once this litter is weaned. Having multiple litters is hard on a cat's body, and causes health problems and shortens their life. If you love her, then you need to get her fixed, or keep her inside and away from all unfixed males.