Major Setback

Just when we thought that things were starting to get a little tolerable, the bottom falls out! Today was a very good day and everything seemed ok, until tonight! I won't go into great detail, but it was the scariest temper tantrum yet! I don't know what to do, there is no rational explanation. I am terrified of what may happen next! We were just at the therapist today and he really seemed to be making progress!!!! Do we only make progress to fall flat on our face? THIS IS TORTURE!!!!!!!!!!!!!!!!!!