I always have a hard time forming relationships because I don't think anyone cares about me.
How long have you felt that no one cares about you?
Since I was a child, I never felt that me parents cared enough about me.
I'm sure you must feel very lonely, but there must be people in your life that care about you. We are all important to someone, even if we don't see it. Talk to your friends and family about how you feel, they can help you understand this.
I can't talk to anyone about it, they just don't get it. I have the feeling I'm the last piece of crap in this world.
I think that if you never try, then you will never know how much they actually care about you. How about getting out of your comfort zone for a bit, and choose one friend to ask? You are definitely important so hold your head up high and you'll start to see it.