I'm not a doctor or expert, but check out something called Complex-PTSD. You seem to have experienced not only a one-time, intense, traumatic event (parent getting shot), you also had ongoing "lower level" trauma (parent in a coma) for 20 years. C-PTSD is most often associated with onging child abuse, or prisoner-of-war like scenarios. The common factor is feeling like you're living in a chronic stressful environment from which there is no escape.

Since it began when you were 5, you probably did what most 5 year olds do, which is to escape through play. Play is soothing and provides one's brain with the comfort of dopamine every time one engages in it. Still, play can become like a drug, an escape from the reality of one's daily trauma. A brain's pathway for dopamine can eventually become so enhanced, that, like a drug, one needs it to keep anxiety at bay.

As you grew older you "used" other things to keep your anxiety at bay- accomplishment, acquisition of material things, the acceptance of others. All are just temporary shots of dopamine, which only satisfy you for a short time. Of course you are never content! Your brain wants more dopamine, and it wants it now, and now, and now and so on.

There are ways to stop being a slave to your dopamine receptors, but I'm not a professional, and don't know much about you so I don't know what will be most helpful to you. It might be best to find a professional who understands C-PTSD, and work with them. Some people have found that Meditation can be very helpful in retraining the brain. You could ask at /r/Meditation or /r/Buddhism if you're interested in finding out more about that. I've also heard of something called EMDR therapy, which can be useful for reprocessing trauma and moving on.

If you repost what you wrote, just as you wrote it as a self-post on /r/Buddhism, I think you,ll get some interesting responses. Buddhism is all about finding contentment through the realization that wanting more and more is just a salve on the wound of discontent.