Have Mental Health Questions? Ask a Psychiatrist Online
Hello from JustAnswer.
No doctor can diagnose autism based on an internet assessment. It typically requires a personal assessment to be able to make such a diagnosis.
Any of the doctors or counselors that you have already seen and made the diagnosis could provide a letter documenting that diagnosis. If you have not yet had the diagnosis, then it would be appropriate to first discuss the issue with your primary care physician, and if necessary, a consultation for a more detailed assessment can be arranged.
If I can provide any clarification, please let me know.