Tobythecat - I am older than you, with Aspergers diagnosed as an adult. I've lived independently for years, had a career for years, but this year it's all gone a bit wrong - diagnosed with depression and anxiety (more than usual, leading to agoraphobia), I've had to leave my job and, to keep my house, I'm continuing to rent it out and have moved back in with my parents at the moment.
My parents have been absolutely brilliant, as they were when I lived independently - they were always there (when possible, obviously) if I needed them, would come and help with practical issues I found hard to deal with, have spoken to people on the 'phone for me when my communication has just failed. I know I'm lucky, but all of the people I know would do the same for their children, or their parents would do similar for them.
It sounds like you're doing well as a rule - I totally understand feeling upset at the last minute change of plans, I have felt like that many times when people think it just 'doesn't matter' that they change plans, whereas I've been ready and prepared for whatever is happening. Have you told your mum how it impacts you, when things like the change of picking up happening?
You're not a burden. I feel like a burden all of the time, one way or another, but am very slowly beginning to realise I'm not.