I always feel like crying

I feel so alone. Although I know there are close friends who are always "here for me", when I need someone to talk to I can't go to them. The loneliness is all I can think about now because I'm sitting in my room alone all day and most of the time. A lot of the time I feel like crying. Even get so close to down to the misty eyes but I can't cry anymore because I never feel better afterwards.
People will tell you crying will make you feel better but the problems don't go away. When I cry I often get sick, or a cold so I just don't cry.
I don't have anyone I can trust because honestly trust is a joke. A lot of things are silly to me because when I put trust, faith, love, passion into something I'm always left dissapionted in myself or someone else. So I'm left alone while I really don't want to be.
All I can think of now is death and dying, the things I've done wrong and what i could have done. But what's done is done and that's what hurts. I realise I hold on to a lot in regards to my past but I don't know how to stop.