I'm so sorry that this has happened to you. It must feel like a rug was pulled from under you. You've spent a year hoping things would sort themselves and you'd get back together, so really - although 15months in - you're actually just in the early stages of grief and realising that reconciliation won't happen. Did XH let you believe that there might be a chance? That's awful and frankly cruel if he kept you hanging like that for a year.
It's ok to feel grief about what has happened, and be sad about the future you'd planned. You are where I was 7yrs ago - in terms of what's happened and kids' ages etc. I really get it, and I remember those times. Ok, I had just separated and things were unravelling (into a God awful train wreck), but still, similar places.
When I was in a funk back then, I looked back to the things I loved doing when I was younger (reading, movies, the outdoors, sports, cooking, music/singing, cross-stitch, baths). Of course, there was a lot that was difficult to do because of time constraints (working FT, full time parenting, no one to have the kids etc) but there were small things I could do to make me feel a little more like myself. Maybe look to doing that...
Are there small things that you enjoyed doing, and that you can incorporate into your daily routine? Can you look to the things you used to love doing before you met your XH? I'd belt out songs on the radio/CD/music apps with my kids when we were getting ready for school, or doing the school run. "Special" and "stupid girl" by Garbage, and "Hedonism" and "All I want" (Skunk Anansie) featured heavily in the early days! I used to enjoy singing when I was young (with friends etc) so it was good to do that with the kids (they like singing too).
The WFH must be hard as you don't get too see many people. I see people at work (I'm a nurse), but am often too "peopled out" and knackered to do much out of work. Is there a chance of you joining any local online groups? Not a local group, but I joined "women only, be kind" on FB and that is a wonderful and supportive group for women. I/the kids do a lot of camping so that is why I joined, but it is for all women. I keep in touch with old school mates (and other friends) via FB and WhatsApp (and I find that brilliant).
Are you able to fit a brisk walk into your day time routine where you can FaceTime or chat to someone? Or do a quick fitness video? Does your XH have the kids at all, so that you can join a local group? Mine didn't (needed supervised visitation when the DC were young) so I had to think outside the box for us. On my days off, friends and I will message each other - even about silly mundane things - and that's helpful for us. Or we issue each other challenges or dares around boring crap like housework or chores that need doing....or coming up with ideas for "use it all up" recipes. PMSL, you're going to think I'm so sad!!
Are you happy to tell us a bit about yourself so people here can throw you some ideas to try out? Or even just be there and listen to you? xx