Creative Depression

I really hate the days where everything seems like it might go alright, maybe I can make it through the day, and then, sneaking up from nowhere my depression hits. It comes in at the most random moments and anymore it's becoming near impossible to cope when it does. It's crippling, I cant move, talk, eat, drink, or sleep, I just want to make myself as small as possible and fade into the background. It's so hard for people to understand this, most people think that depression is a constant feeling of being sad. Its not, it can be part of it, but that's not all. Some days it's just feeling isolated, and scared. Others its blissfully peaceful, those are the scary ones, when I feel at peace, like everything will be ok, no matter what, like if I just close my eyes and push the gas peddle all the way in and let go of the wheel. It seems like these days get more and more frequent and it effects my social life, my relationships, my work, and my home life. It filters in at any point, and it really scares me anymore. I don't know what to do.