I'm not sure I understand what you put above. If you think you have to be 18 to go to the emergency room, you don't. Maybe that is not what you mean. It does take courage to go to the ER. Another option is to go directly to a psych emerg, if there is one in your community.

There are crisis phone lines that specialize in helping teens. Here is a link. Boys Town | Hotline

I don't recommend texting, but it is an option. On the internet, there are other resources. If you identify yourself as under 18 (and you don't have to,) they will be extra concerned about helping you access resources that are hard for a minor to access. I think you might find it good to talk to someone in a live context.

It is true that, if you sound like you are on the verge of self-harming, they may try to trace the call and send police. They don't jump to that conclusion right away though.