Over the course of about a year, my meltdowns lead me to getting a wall section in my bedroom replaced because I always punched it when I got angry during a meltdown. Just that one spot, over and over again, and it eventually crumbled. I'm not proud of that in any way, and since that was replaced I have been able to get a better hold on the anger that builds from meltdowns.
Though like you, I now tend to take it out on myself and sadly my mum tends to bear witness to a lot of it which makes me feel bad because she doesn't deserve that. She's never done anything but look out for me.

I've actually got my first appointment with an Asperger's support clinic this afternoon. Hoping they can provide some support for either myself and or my mum. Sadly, it means going into the city which I can almost guarantee will result in a meltdown.