Have you ever been evaluated for Asperger’s? The anxiety and extreme reactions to sensory stimuli and stress could be symptoms. It would explain the “meltdowns” just about completely.
Have you tried working with a CBT therapist? That is regarded to be most effective for anxiety.
Check out hypersensitivity too — that could be another potential explanation.
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism