Wolfgang, you and I must be quite a bit alike. I've struggled with the same issues for a while (since jr high) and now in my early 20's, I still don't have the answer. I slid through college with the bare minimum, and now the only thing holding me motivated to keep my job is the desire for privacy & independence from my parents. I can barely make it to work on a consistent basis, much less do laundry, pick up after myself, or bathe regularly. We won't even talk about the state of my car at the moment. I don't have friends of the sort that other people have because they're either too much effort or too invasive.
I have absolutely no motivation to do anything that requires time, effort, energy, etc. that I would rather spend elsewhere. It seems to be because none of it bothers me. The second any of does though, from a picture frame tilted 'wrong' to a week old bag of trash in a corner, start to bother me; I suddenly have the motivation to "fix" it ASAP. But until that moment of negative stimulus, I just don't care.

I wish I had some suggestions for you but unfortunately I have nothing to offer but an 'ear' and the encouragement that you're not alone. Maybe one day I will have something more.

Also, props to you for being honest & transparent in your quest for help in this post. There will always be others who 'shame you' due their own lack of ability to see a situation from any other perspective than their own. Don't ever let any one else's ignorance get you down.

Here's a favorite quote of mine: "If you have a complicated job, hire a lazy person for it; he'll always find an easier way to get it done."