Not fitting in at work- feeling isolated

Hi, I am feeling very isolated and depressed about not fitting in at work. There was an incident on Friday which made me feel very excluded and made me more aware of how isolated I am- I thought I had got over it but I am not coping at all and feeling extremely out of place. 

I work in a lab (where I am meant to do a PhD) since September- On Friday I was asked last minute to image some samples on the microscope for someone else, which was a bit stressful and frustrating as I had offered to do so before and I had specifically planned to work all evening to finally get some of my own work done- the microscope was only free from 5 afternoon onwards on the Friday and I had planned this since the week before. So I started off with the other person's samples and of course ran into an error with the microscope, which I was struggling to solve (I'm new to this microscope)- the person that I was helping then just left me alone to troubleshoot and image their samples - turns out he went to have dinner at a Chinese restaurant with everyone else from the lab whilst I was left on my own to sort out the microscope and take images of his samples. I don't think it was deliberately unkind and I did remember then that they had mentioned something about a dinner on the Friday at the beginning of the week (no details) and that person did know that I struggle with social events and eating out and I had said that if they did plan something to not look out for me specifically with the time but to please let me know so that I could spontaneously decide if I felt up to joining. So I feel like this is my own fault and not an unkindness by others but I still felt awful and very alone and isolated. I also feel guilty that I was frustrated about having to help out- I think it's because over the past months I spent a lot of time helping everyone so that I ended up completely burnt out and never got my own work done- I just wish I had known about this work that the other person needed sooner so that I could have planned but I think the person probably also didn't know that this needed to be done urgently. 

However this incident has just made me realise that I feel very apart and do not feel like I am part of the group. When I first joined the lab everyone just ate at their desk quickly whenever they had a few free minutes. I was off sick for quite a while and when I came back new people had joined that lab and it has become a habit now for people to sit together to have their lunch together. I find this quite overwhelming so it took me a while to even try sitting with them for a bit (I find eating with others very difficult but I just joined them after)- I tried twice to sit with everyone but it made me feel really stressed out- I could not connect to the topics being talked about and had a very strong urge to leave. It reminded me of feeling like the odd one out at school. 

Also tomorrow a lab pizza evening is meant to happen to celebrate a recent publication- everyone seems to be really looking forward to it and I should be too but I just feel very stressed out by it- it just makes me feel weird and abnormal that I am stressed about it and I don't know why I find all this so hard- I just don't want to/ feel up to joining. I already struggle whenever we have a piece of birthday cake together for someone's birthday. I have now also found out that everyone is expected to be at the pizza party (mandatory) and this makes me feel super uncomfortable as I had hoped I could either not join or just join very briefly. 

I feel very sad and lonely and isolated. The people I work with are very nice but I feel out of place. It's been so much harder since I left Cambridge (where I went to university)- I was different/weird there too but there were lots of people that were different in various ways so I fit in and I found some likeminded people and made some very close friends (which I am still in touch with virtually). Also in my previous labs I connected very well with some of the people and I felt much more included- I am still friends with previous lab members and we had great times together (takeaways together in evenings and lots and lots of fun discussions about science). I don't know if it is because I am so depressed and burnt out that I am struggling so much to fit in here or if I just don't fit in this group. I miss Cambridge so much. This weekend has been very tough- I thought I was ok but I have been so depressed that I just ended up comfort eating and binging which made me feel even more awful: I struggle a lot with food- I recently unintentionally ended up extremely underweight as I struggle with digestion, lack of appetite, ARFID type issues and end up if I am not careful eating the same handful of foods over and over- I did manage to gain back all the weight while off from work (I was so unwell I was almost hospitalised) but I also struggle with overeating and binging when I am stressed as I try to seek comfort and self soothe. I am also so frustrated that whenever I seem to try and listen to appetite and do not have digestive issues I end up loosing weight... this then also results in overeating out of frustration, more nausea and more overeating as I get very out of touch with my body and feel nauseous anyways so that I don't care if I feel even worse. Sorry I am disgressing... but it is all a huge mess. 

I just don't know what to do as I feel so utterly alone and out of place at work, not to mention incompetent. I am not my usual self and haven't been able to work as well as usual and just haven't achieved much the past months. I feel lost and like a failure. I am so unhappy and I miss Cambridge dreadfully (probably also a sign of my unhappiness- maybe it wouldn't be much better there, though I do think things would be easier- it is so much harder here to fit in and meet people here). I also haven't been sleeping much the past days which is not helping with a positive mindset- I just feel so nauseous and stressed all the time-maybe that is why I don't sleep... 

I don't know what to do about my feelings of isolation at work- I don't know if I can fit in here at work- I didn't have such a hard time in previous labs. I am so deenergised and burnt out that I am struggling to try harder to fit in- I have no energy for masking at the moment. I don't know what to do. 

I'm really sorry for the long post, I think I just really needed to talk about this- feeling very low right now. 

I forgot to mention- I am most likely autistic, but still awaiting diagnosis - so people at work do not know about this (except one person that I confided in a while back).