I think that there are some many approaches to chapter writing, and what works is so different among individuals. Some people like to outline each chapter prior to writing, with lists of sources ( or have supervisors that require that). Fortunately for me, my supervisor has not done this, as it would be a very horrible way for me to work....I write ( madman phase) and ideas often occur to me as I am writing--much of the 'aha!' or 'Eureka' of insight occurs as I am struggling to piece concepts and ideas together, and sort out my own thoughts. Often its not until its own paper, that I see a big conceptual hole, or a hole in my own thinking that can require some backtracking to deal with. ( I am struggling through such a conceptual hole at this moment!) I am, just by way of reference, writing up, and its sometimes hairy to realise that there is a bit of fuzziness or concepts that don't tie up well in a theoretical framework, and its back to the slog of working it through....
Those moments of feeling clueless come and go throughout the PhD, I think the bliss of not knowing the vastness of what you don't know is what enables anyone to even start on a PhD, and then as you go, you realise how much more knowledge and information is out there, that you never even remotely knew existed, and this can be daunting, and force you to take account of wider bodies of knowledge as you go. I think that those moments of as you said " I don't know what I am saying anymore" are the ones that lead you to the deep research, thinking, etc, that lead to the originality and pushing of knowledge that a PhD is all about. It can be frustrating, but it leads you on deeper and deeper....the PhD seems to be like a layer of circles, you spend a lot of time perhaps circling around and back to ideas, etc, but hopefully always with more knowledge, more ideas, more links, whatever, so that each time you revisit something, you see it slightly differently!
