Previously Denied, Condition Worsened

In my late twenties, I was hit by a car as as pedestrian which left me with several injuries, however due to my education I was denied because of the fact that the evaluators said I could perform a similar job in my field. It has been difficult over the years and I have not been able to keep the same employer for very long each time due to several issues. I have suffered from addiction to pain medication because I was forced to work. I am now 41 and my conditions have worsened immensely. I am unable to stand or sit for long periods of time.I did have internal injuries,but most were lacerations to the liver, which regenerates itself. My main conditions which include lower back pain and depression have hit an all time high. The most disturbing part for me is that I suffered a major head injury which required over 100 stitches, anti-seizure medication, and short term memory loss. It impairs my ability to hold a job, being taunted by supervisors leading to further depression which just continues the cycle. I have been under medical treatment for pain, depression,short term memory loss, pain medication issues, insomnia, etc. I have also been diagnosed with fibromyalgia and survivor's guilt. At my last employer I was asked by a supervisor if I had a learning diability due to the short term memory loss I suffer and pain issues issues have intensified with age. I have tried my best,but with age, my conditions are becoming unbearable. I have seen several physicians that have said they see me as disabled and I continue to be treated which I will probably have to the rest of my life. If I file again, it will be my 3rd time. I am not working now due to the fact that I either cannot perform the work, lift, file,or pass the educational tests in. A timely and satisfactory manner. It is very discouraging and I feel it is time to try again due to the worsening of my conditions. Please advise.