Slipped Disc!

A spinal disc herniation, commonly called a "slipped disc", is normally a further development of a previously existing disc protrusion, a condition in which the outermost layers of the annulus fibrosus are still intact, but can bulge when the disc is under pressure. This is a summary that i got off the net.
I'm currently diagnosed with slipped disc, a very painful problem with the back, which mostly affects mostly people in the 30s or 40s. So i got a very big burning question here, how can a guy in his early 20s get a problem like this? You might understand after reading this.
Causes of a disc herniation can include general wear and tear on the disc over time, repetitive movements, stress on the disc that occurs while twisting and lifting, or other injuries. Well, i think that answers my question. There are 2 possibilities that causes my slipped disc. Here are the possible 2,
1. When i was younger, maybe about 15 or 14, i had this back injury because i did not warm up before my baseball training.It really hurt me for about 3 months, causes me to wince in pain when i was training, no matter how much i warm up, quite similar to the problems i'm having right now.
2. When i was working part-time in a hotel, i always stressed my back muscles by carrying many heavy stuffs, and always have backaches the day after because of all the carrying.
Guess all this has taken a toll on my back. Well. I decided to take as much care as i can to my back from now on, so as to recuperate from this injury and be healthy again. And this is my advise to all young aspiring sportsmen/women out there to always warm up and take care of your body, always listen to your body. Stop whatever you are doing when you can't take it. With this i'm signing off, Holla!!