Ya I have big trouble expressing myself in words normally, let alone on this subject.

It helps, at least for me, to type it (aka post here)... sometimes just typing/ranting on the board helps me to better understand what I'm feeling.

I don't know the person you're thinking about, but do consider telling them a general thing, saying just that... (as you said)i feel terrible. suicidal thoughts. I want it but I have no clue why", maybe then saying, you're having trouble explaining it completely even to yourself and it's really hard to talk about, ...
or try what you're already doing, trying to think of how to explain it.

The thing is, at least for me, a lot of what I feel doesn't make the most clear logical sense, and when I say it its kinda like um that sounds wierd, or wrong, or wow they're going to think I'm stupid...
but I think, part of that's just embarrasment, and to just try to express as closely as possible what you feel even if it's general is better than remaining silent, and maybe even the best way to start conversation.