L.H.
Short answer - yes you are completely normal to feel that way and lots of others are right there with you.
My dear friend has 4 on the autism spectrum. I know 2 therapists come to her home (she homeschools). Her children range from 4-15. She will call me when she is spent. She is also very active in co-op learning, American Heritage Girls, Trail Life, service projects, orthodontist stuff, medical appointments. She is a professor at a nearby college and teaches at night so her husband can manage the kids. I am amazed and humbled by her on a weekly basis. She calls me occasionally, exhausted and wanting to just close her house doors and retreat. I think it's understandable.
Know that you are normal in your dread. It is so nice to be in charge of our own schedule and time. I'm going to make a suggestion that might help. For my family I set apart half a day where we do not make any commitment to anyone else. It is our family time. If there's a death in the family or some other serious circumstance I will forfeit that time. Otherwise it is treated with more importance than a dr appt. Maybe you could have that time to look forward to with your kiddo and it would give you a sense of control over your precious time. The older I get the more I realize that time is our most precious resource.
Blessings!
L.