Mid-stage PhD student lost motivation I'm a PhD student in literature who is nearly half way through my third year. 

Recently (last month or two) I feel like I've lost all motivation to work on my thesis. Instead of treating it like a normal 9-5 workday I now go in late most days and procrastinate for a few hours before starting any actual work. 

I'm not up to where I wanted to be in terms of chapter drafts at this stage of my program, but instead of this motivating me to work harder I just feel disheartened and like I will never catch up so why try. These defeatist thoughts make me feel even less like working so i end up in a vicious spiral of not working, guilt about not working, no motivation to work, more not working.

I feel overwhelmed by the amount of material I feel I still need to read to be 'across' my field and don't have a good sense of how im going to tie my various chapters into an coherent piece of work connected by an overarching argument and theoretical framework. 

I have been managing an anxiety disorder throughout my PhD, and have in the past suffered from depression. I struggle to know if these feelings mean my overall mental health is deteriorating and that's what's causing the negative feelings about the PhD, or if it is the fact that I spend most of my time doing/thinking about PhD and so if I feel good about it then I feel good most of the time, and if I feel the research is going bad I feel bad most of the time. I've been sleeping to avoid going to the office and feel down about the thesis but this doesn't carry over to other aspects of my life - which leads me to think it's more phd-caused than mental health but who knows. 

My supervisor is unaware of the underlying mental health issues. I struggled early on in first year which lead to me telling her I felt overwhelmed and she instructed me to take a week off, but I didn't outright disclose the anxiety. I've tried to flag recently with my supervisor that I feel a bit lost and behind, but she didn't seem overly concerned and I think I downplayed the extent to which this is impacting on my day to day work on the thesis. I wonder if I need to be more overt about how much I'm struggling, or disclose the underlying mental health issues. We have a very good r/ship which often feels more like a friendship than a supervision - which has it's upsides as well as downsides when it comes to something like this as I don't want to let her down or for her to be disappointed in me by disclosing how much work I'm not doing, but also don't want to ruin the friendly vibe by getting all serious with how I'm feeling re: thesis. I'm worried that even though she seems happy with where I'm at draft wise, she thinks I've read much more than I have because she doesn't know how much time I'm spending avoiding the thesis. 

Part of me feels I should just 'get on with it' and if it is mental health as the underlying cause this is not something my supervisor should have to manage anyway so why bring it up. Another part of me feels I should be more honest with her about how much I feel I'm struggling with the thesis and not worry about seeming needy or incapable. 

I feel like the time toward completion draws ever closer and yet the amount of work I need to do to finish doesn't progress at the same rate. I feel like I don't work hard enough at the moment to finish on time, and this feels both terrifying and paralyzing. I've read lots of blogs about procrastination tips and such but struggle to put them into action. I've also read lost about mid phd slump/doldrums so logically know this isn't uncommon, but at the same time I've lost some of self-confidence to think I'll be able get through this phase like others have.
Gamification of your time-management method maybe an answer. Gamification is the latest trend in the Internet that involves putting game elements to motivate users to engage more in a website's activity. First of all, you can set experience points to each task, and exp requirement for each leveling up, badges for completion of tasks. Be sure to take care of your health while you do this.

About anxiety, procrastination and other symptoms, there are a number of reasons:
(1) The slow monster
(2) The not-believe-in-future monster
(3) The exhaustion-of-thoughts monster
(4) Nightmare and risk monster
(5) Anger monster
(6) Crying monster
(7) Self-restriction/limiting monster

So, these are the monsters that you need to fight in your adventure. If you can fight off them, high chance you will be able to finish your thesis. Good luck!