EDIT: I should clarify this is not the first draft of my PhD, it's the first draft of my upgrade document to go from MPhil to PhD.
I have been working on my PhD for about two years now, it is a six year part-time program. I have a very good relationship with all my supervisors and they are very supportive. I am fortunate to be part of a good university which is open-minded and free-thinking. I also have attracted the interest of a well-known external academic who is an authority within the field and who wants to be involved. I am very lucky.
The problem is that I am just not that interested or convinced by my research [chiefly its significance]. I have to submit my upgrade document [MPhil > PhD] in about five week's time, and the viva is a week after that. I have written a draft document which is 12,000 words and my main supervisor has written a lot of comments which are suggestions for improvements. The issue is that I do not feel that interested or compelled to work through them.
I am under the impression that my supervisor is not that convinced by my research, even though she keeps saying she has no concerns. I feel my research is too vague, too broad but also too overbearing. It incorporates three disciplines [at the advice of one of my supervisors], disciplines A B and C. Discipline A I am not that interested in - I was for my master's but now I find it quite tedious but it is quite an important part of the whole. It is a well-worn discipline and feels rather old and stale to me now. Discipline B is quite new and interesting, I have published within this discipline. Disipline C is very new and up-and-coming. I find it quite exciting and my supervisor has written the least amount of comments about it in my draft paper, which I take to mean she has the least amount of complaints about it [she has a lot of comments to make about dispclines A/B]. She has also said that discpline C is a 'key' part of the PhD.
I do not know what to do. I am really not that interested and the whole thing seems so daunting. My PhD focuses on A and B mostly with C being only a feature, but I am wondering whether I should switch things round entirely and make it more about C. I feel I will not really be able to convince my panel about the significance of my research in the viva if I am not excited about it or convinced myself. In my master's I was always keen to research and write, now I am not, but I know I would be if the topic were carried out a bit differently.
What shall I do, how shall I regain interest? My PhD seems rather fluffy and not sharp enough. Additionally, I am daunted by the scope of the whole thing: it seems too large to work through and 'bigger' than me. I am kind of at a loss for what to do.