I just.. don't want to exist

I don't necessarily have a good reason. I just feel like not existing. I'm a very empathetic person so I'm always there for my friends and family, even strangers. And I know my suicideness isn't anything good and that I should seek for help or talk to someone. I just..can't? I don't know how to open up to people, I don't trust anyone with such things. So I just keep going on and do what I have to do whilst still am there for others. But I'm so tired. I'm only 21. I just needed to write it down somewhere.