Anon, you won't instantly "get" a diagnosis. I had to wait a year and a half of seeing EIP psychs (for psychosis), CMHT psychs (local mental health), CATT psychs (crisis team) AND a CPN AND my own GP before getting one. Having a label for yourself doesn't help matters, in fact it makes it worse. Yeah, you can name it, but it doesn't mean you will instantly find a cure.
The first step is seeing the GP, who can see if any more help is needed. They may put you on an anti-depressant, but bear in mind the first one doesn't always work, and cost does not mean it works better. Also, unless it is an URGENT referral (in my case, well, I'm not going to go into it, but it was especially urgent) you might be waiting up to 3 months to see a psych OR a CPN. So honestly don't think this is a quick thing, it is a long drawn out process, to ensure what they think is wrong with you, is what it is, and not something else, which if mis-diagnosed (as can happen if rushed) can cause more harm than anything. But go to your GP, they can start the ball rolling.
Also, attempting to diagnose yourself online with a "test" that takes nothing into account causes more harm than good, as you can then mis-diagnose yourself, and psychosomatically start exhibiting symptoms that have no bearing on your true state. However, from what you have said, it is obvious your are at least suffering from depression, due to my own experiences. For now, stick with that.
I also agree with antimatter and littlepotatoes. Self-diagnosis is scary. I don't even bother finding anything out about stuff as I don't want to cause my mental state more hassle (but when I did look at what I had, I fitted EVERY point of ONE of the 10 point diagnostic tables that can be used, and this was after my diagnosis, and that scared the **** out of me) If it makes you go to the GP, then go. Book a double appointment so you have more time to talk, and write things down to remember them. Right now, your main concerns are the depression, sucidal ideation and not eating well. These, and these ALONE should be mentioned.
By the way, I know whereof I speak, I am a nutter. I've seen the various psychs and teams at various times (in hospital, at home after freaking out, in treatment rooms, etc etc) I have a diagnosis, not because I ASKED, but because it enabled the people treating me to handle my care in such a way that it isn't a detriment. Right now, this isn't your concern. Yours is to get your arse to that GP and let them know so they can help you.
(I have borderline personality disorder with pseudo psychosis. I also have a few bi-polar tendencies, but no-one fits in a box. Remember that, NO-ONE FITS IN A BOX. Take this ONE step at a time, do NOT look at self-diagnostics, do not look up what it could be and might be. Deal with what is REALLY there, currently NOW)
Thought he was 19... really he's 14