Ok, thanks again you guys, your posts are really helpful.
I'm pretty relieved, I just got off the phone with my pastor, and he's behind me in this, more so after I'd told him I'd been at the point of being ready to use a suicide plan for the next day throughout most of Monday. He was pretty concerned hearing that... but was glad I'd made the appointment, which was apparently what he planned on trying to get me to do the next time we talked. I was afraid no one would understand, saying I should just see my PCP. That's how my mom is... which is a huge frustration, but it'll really help to have my pastor with me in it, especially since my mom really respects his views.
The one thing I'm still a little off on is the fear of what this psychiatrist will think/do when/if he realizes how suicidal I've been lately. My pastor said I shouldn't hold it back, but he was concerned about that too, so I'm a bit more concerned about that aspect than before.
But still... I feel much better, and I guess I'll just face whatever happens... what can it hurt at this point, anyway?