Some from dreams, certainly, though I suspect that that would happen more often if I was writing long form fiction full-time, as my head tends to dream about the things that occupy my attention. I get a lot of ideas from conversations with people, as well as considering "What if...?" questions in my own life. Some ideas I get from mass media, expecting that the plot will go one direction but then find it goes in another. In those situations, part of me really needs to complete the story as I imagined it. That can be in the form of direct adaptations - what you'd call fan fiction - or just in situations similar to what was set up in the original book, film, radio play, TV show, et cetera.

Indeed the story I am writing is really just a long line of dreams that are following a plot that I have no idea where it is going.In the morning I take out my book and write down what happens next in the story and it can get really frightening cause sometimes the story is in a nightmarish mode.

That's awesome! How cool to dream a story, it's like you're reading it, not knowing what's going to happen next.