Let my autistic child down today and feeling awful

I’ve been posting on here recently so sorry for another sob story.

Currently staying in a crisis house due to a mental breakdown (bipolar) but still get to go home when I want. I have a profoundly autistic child at home with my partner/his dad.

I have been seeing him for short periods every day because I’m struggling so much. But Saturdays I always take him to a SEND swimming session, it’s sort of ‘our thing’.

I was being picked up at 11:15am. I woke up at 9am screaming from the most horrific nightmare and felt so exhausted. I got up to make coffee and start getting ready, but before I know it I’ve sat on the bed and fallen back asleep and it’s 11:15am and they’re outside to pick me up. The session was due to start in 15 minutes.

I rushed to get ready but that took 15 minutes and by the time we got there we were half an hour late so he only got 30 minutes instead of the usual hour.

My son is non-verbal with learning disabilities so I know he didn’t mind, but my heart is hurting because I feel like the most unstable, unreliable mother, and I’ve been thinking about it non stop all day.