My fiance (26f) has broken up with me (23m) but we still have to live and work together. She wants to be “friends” but I desperately want her back and can’t cope now I realise it was mostly my fault

My fiance started acting poorly towards me as she checked out the relationship due to built up resentment from me not sticking up for her when my mother would bad mouth her when we lived in my mothers house. At the time I was doing what I thought was right. I was keeping the peace, comforting my fiance but not addressing anything with my mum. She is a textbook narcissist and anytime I have ever tried arguing with her in the past she never apologises or accepts anything and then makes my living situation worse which I didn’t want while my fiance was living there. Upon reflection I think it was more so the childhood trauma of sticking up for myself to her and my fear of confrontation that stopped me from speaking up to my mum rather than the logic of keeping things peaceful. I didn’t realise it was affecting my fiance as badly as it did until we had moved out. We booked our wedding after we got the house so I assumed everything was fine and she was just stressed about moving that was causing the bad behaviour.

When she would snap at me and be mean due to stress wether it was caused by me or not, I would do everything to make her less stressed. This stress response I think is from her own childhood trauma from her own narcissistic mother. However thats what mother used to do to me as a child and it would mess me up. So when my fiance would do it would really hurt me. She always used to apologise for it but it got so frequent and so intense that I once said “whats the point in apologising if you’re just going to do it again in 5 minutes anyway” and since then the apologies after snapping would be much mess meaningful or never really come and I started holding the grudge more and would go in an awful mood even if she apologised. Again this is something I didn’t really realise I was doing at the time but upon reflection it’s something I need to work on and become more aware of when I’m “punishing” her with my bad mood after she has hurt me.

She started being more cold and distant each day for months which caused me to go insane. Thinking shes the problem pulling away, dropping communication and affection a little more each day, new friends popping up all the time, their pictures replacing mine etc. it drove me crazy. I think would anyone tbh but I think it did to me especially because of how attached I was to her. She had been my only friend for the last 3.5 years and I basically gave up my life for her which I didn’t realise I was doing at the time. She just made me so happy I couldn’t help but want to spend every minute I could with her. I truly regulated my emotions off of her. I could not be happy unless she was etc.

Only now after it’s ended do I realise I was the mostly the problem and if it wasn’t for my actions we would still be together and getting married. I can’t put into words how much I love her, I had never experienced happiness, safety and security in any comparable way until I met her. She gave me the best days of my life by far. My stresses and anxieties melted away whenever I would be around her and I put 100% of my effort into her even as she was checking out. Now she still wants to be friends as we have to live and work together still but I desperately want her back and I hate myself for messing it up. I don’t know how to cope without her as shes all I have and I want to tell her how I feel all the time but shes the one person I shouldn’t be talking to about it. Everything reminds me of her and I cry multiple times every day, I feel sick in my stomach all day every day and I can’t eat, I don’t know what to do.

If anyone has any advice somehow for this situation that would be great?