My three month old kitten has a very wet sound when she breathes?

She was on twice daily antibiotics for two weeks, and is on twice daily L-Lysine for her immune system, but she still sounds like her lungs are full of fluid. She is quite active, playing with her brother and our dog (her best friend), but sleeps very deeply, almost stops breathing. No one seems to know what is going on, including our vet. Has anyone had a similar situation?