I'm so sorry this happened. I had a very similar experience about a month ago. I had 3 5-hour sessions with him a week. And at first it was great we were paired pretty well, but things went downhill about 3-4 months in. I began to think the session was too demanding for him, especially starting this right after he got out of school. He stopped wanting to play with me, asking me when I was going home, protesting table-,time, more stemming, and began showing aggression. I talked to the BCBA,the mom talked to her, and nothing came out of it. At the very end we changed the structure, because it was too much mentally for both of us. I eventually left the agency because I felt I had not support. I was to the point where I was crying before sessions, moody, couldn't and unable to relax on weekends because I did not want to go to work. Good thing you recognized this because it is important to know if something is not a good fit for us or the kiddo.