Yes, it is very possible to "slip down" the spectrum. I think that I have done the same in some regards, especially after finishing college. Putting on the front is challenging, and eventually it gets the better of you in one way or another. Eventually, you start realizing that you need to find ways of living with the level of disability that you have. There really is no changing it. It could be possible to work on some skills and regain what you had before to some extent. However, it is likely that what you thought you had before was really somewhat of an illusion and you were never as "normal" acting as you thought.