Work, burnout, not sure what to do, stuck and exhausted

Hi, I'm a bit desperate at this point as I seem to have managed to get myself out of one bad situation straight into the next disaster. Essentially I recently took a new job in August and moved back to the UK. Before this I had been working in a lab in Germany for a year (I am a neurobiologist) as I was hoping to do a PhD there but I ended up exploited and working unpaid for 6 months, before being employed part-time for 6 months- plus there were other issues. I had a hard time in Germany and my health suffered and I ended up physically unwell and burnt out and depressed but I took my last energy and applied for jobs whilst still working. I would have applied for a new PhD position straight away but it was the wrong time of the year and most deadlines were past- therefore I ended up looking for research assistant jobs in a lab so that I could work for a year, recover and also apply for PhDs in the meantime. I chose to move back to the city where I had gone to university as I felt at home there and I thought the job I had been offered there might involve slightly less responsibility and a better chance of me recovering than some of my other options. I had no break between my job in Germany and the new job and I started work in August utterly exhausted wondering on I would cope- the novelty of the new job somehow got me through it but I soon ended up working extremely long hours: 1-2 days on most weekends and for a few weeks I often only got home at 11/12 at night. On top of this I am really struggling with food and digestion (ARFID type issues) and by this time I was only eating eggs, toast, carrot and apple and I was loosing more and more weight - I tried to expand my diet half-heartedly but I just did not even have the space or time or energy to tackle this. Whenever I had time off I felt physically ill with exhaustion. 

At some point I realised this job is being completely counterproductive at this point: I am not getting any intellectual satisfaction from it and it is quite frustrating to only assist and never see things through (which would be ok if I was working more normal hours). I am not getting a qualification from it. I have no time for anything- no time for relaxation or seeing friends and no time to apply for a PhD which is what I really really want (and the deadlines are in December/January). So somehow on top of everything I tried to start applying for PhDs as well... I managed to do some applications and even ended up travelling abroad for an interview. I have had very little sleep and it was all crazy busy. Things settled down a little at work as Christmas was approaching and I felt so burnt out and I don't think I have been very productive recently and people noticed that I seem exhausted. At some point I also started expanding my diet as my body was not taking it anymore which is a positive thing but it also means that my digestion etc is all over the place and it is further disrupting sleep when I actually have time to sleep. 

I now finally had time off for the Christmas break a week ago (actually ended up taking some leave so that I could take off early as I was no longer needed)- I thought the rest would do me good and I would regain some energy and be able to work on some more applications and prepare upcoming interviews. So far I have done no work and just tried to distract myself with puzzles, lego, origami etc. (sadly I am injured and cannot do the outdoor activities I love). However I am growing increasingly depressed and tired with each day (or so it seems)- Even when I started the vacation I thought 2 weeks would not be enough for me to recover but it is becoming more and more clear that it really isn't going to work out. I am not sure what is wrong with me and if I am so so tired and exhausted and growing more and more depressed because I have not rested enough or because I need to drag myself up again and start doing something productive like dealing with my PhD applications. This is the one thing that kept me going as I really badly wanted to be able to start a PhD next autumn at latest- I really hate my current job and if I do not take care of these applications I am likely to be stuck in this job (or a job like this) for a second year. However I have lost my drive. I can't even work up the energy to even start contemplating working on these applications. 

I have no idea how I am meant to go back to work in less than a week- I feel so burnt out and unable to cope even when not doing anything at this point and I just don't know how I can cope. I am thinking of asking to take a few more days off but I am not sure I can do that and even that seems not long enough to recover from my profound state of exhaustion and burnout (I actually haven't really had a break in ages...)- I think if I somehow force myself to go back to work (if I manage to drag myself there somehow), maybe some residual energy will kick in and keep me going for a little while longer- but at what cost? I also urgently need to take care of my food issue as I am so severely underweight- I am trying but for that I also need time and space. I am worried that I will loose my job if I try to take more time off or if I end up on sick leave. I am still on probation and I also hate doing substandard work. The issue is also that I have a lot of work that I need to do in the new year that one I get started with will not be easy to just interrupt to take a break and it will likely involve considerable weekend work too... 

One option would be to move back home to my mum who is outside the UK- however I am not keen on this option as I am not sure I could cope with another move- I have bad memories of being in Luxembourg and back home and I feel much more comfortable in the UK. Also it could possibly lead to issues due to Brexit if I want to return to and stay in the UK (and I really do want to stay here). Plus I am worried how this would look on my CV and I would end up with a long gap between this job and starting a PhD if I got an offer... it feels like giving up and like a huge failure to move back home and I am not keen. Also living with my mum has been problematic in the past ... but then again I don't have many options? 

If I am to stay in the UK I need to have an income so that I can pay the rent. I really wish I could just have a longer break now so that I could have a chance of recovering but I have no idea how I could put this into practice and how I could make my work more bearable and less exhausting. Should I contact the 'disability at work team'? I'm not sure though if that is appropriate as it is hard to know which of these issues are related to being autistic...? And I don't know what adjustments could help me...?? I also feel like I should be able to cope. 

At this point I am just utterly depressed and feel stuck in a situation which feels like it has no good solution. And I have lost all energy. I'm so sorry for the long long post. 

I just realised I should probably mention that I am autistic- I was diagnosed a few weeks ago. Thanks so much for listening.