Why Would A Young Female Develop Lower Spine Disc Degeneration?

I just got discharged from a hospital for a disc degeneration of my lower spine. They couldn’t figure out why or gave me a plan on how to fix it. Just bedrest, pain meds and ice. I don’t understand how I got that. I’m a 20 year old female. I do however have many chronic illnesses which I know can lead to unusual predicaments. I would just like to know why and what I can to to fix it.