If you are really this suicidal, you might want to seek some kind of intervention. I'm not exactly pro-hospital, but if it gets really bad please at least mention it to a friend. There are a lot of decent medications out there that are good for short-term crisis intervention that will take the edge off of these feelings. If you really don't know where these feelings are coming from, then it's possible you have a neurochemical shortage of some kind -- I speak from personal experience. When I get this terribly down it becomes a struggle, and I start to focus on things like:
How well am I eating?
Am I getting enough physical activity?
Am I exhausted and not getting adequate rest?
Am I getting a health dose of work vs. leisure with activities I really enjoy?
Am I getting enough sun?
Am I spending too much time alone? Have I had physical contact with another living being recently (whether it's a hug from a friend, a partner to cuddle with, or simply petting an animal, etc.)?
If the eating thing is difficult, then I recommend during your better-feeling moments you think of an easy, relatively healthy go-to food that helps you feel better when you're down. It should be something that is pretty effortless. I get really down in the winter but I have managed to take the edge off a bit this year by paying attention to how nourished I am. I've noticed that lacking B vitamins, vitamin D, and magnesium, phosphorous and calcium all negatively affect my emotional state. Fortunately liquid D3 is cheap to buy now, and most of the other nutrients you can get from eating dark leafy greens.
The other thing is... does your depression/anxiety come from a sense of threatened survival/fear, or does it feel more like there are emotions that are difficult to work through? I've learned that my depression is often triggered by something unsuitable in my life, and my body will react to this before I even logically deduce the problem. If it's fear based then something in your environment could be triggering you. If it's emotion based, then maybe where your life is at is not best for you (i.e. job that you don't enjoy, something about your home life, etc.)? I'm someone who tends to push things aside and live in denial land if something is not working, and drag it out for as long as possible, but eventually my mood crashes and forces me to examine the situation.
Please turn to a friend a.s.a.p about this! If you are having heavy suicidal ideation it's going to really drain you further. Find a way to get this out of you instead of holding it in. Write it down, talk it out -- anything! Just don't keep it internalized.
The artist's job is not to succumb to despair, but to find an antidote to the emptiness of existence. -W.A.