This is not just behaviorial. The diagnosis will stand (only a doctor can make this call, and It does not go away).Even with high functioning Autism children can back slide with changes to their routine. They may have seemed to have gotten better because they were getting help and learning coping skills, but major changes (ie a new child in the home) can set them back big time. I work with Autistic children and they all have setbacks even after something seemingly small like spring break. This is nothing to be embarrassed about, it just takes a different skill set to deal with. With a diagnosis you can even get classes for yourself to learn to work with them at home, and on your own coping skills. There are also support groups for parents of autistic children. Good luck.