I'm going to refer to something in your original post. I'm not all nicey nice today, but I don't mean to be mean either. Let's say, someone, like myself, or especially my son, came across this post. He has severe learning disabilities, and I know my i.q. would be very low. You say you know you are quite useless and you don't see value in living. I've been struggling with this issue for years, worrying that I'm not worthwhile just because I can't compete on the same level as someone with a high i.q.
It's disconcerting to people like myself to make assumptions we aren't worthwhile. Even developmentally delayed people have worth. Re-think what it is that is valuable, truly valuable at the end of our lives. Have we helped anyone, animal, situation, etc., done our best to change in ourselves what we should, in order to be beneficial to this one and only life we have? Just my thoughts.