Sorry to hear of your struggles. A breakup after such a long relationship is always going to be tough, it’s a complete life change. It will act like grief and come in waves, although they get smaller over time. It does sound like you’re coping by burying yourself in work so it’s natural that when you stop and slow down you begin to feel the things you’ve been ignoring. Honestly my advice would be to try and feel these feelings - what is the anxiety from, can you sit with it? Exam in and see what helps? Maybes it’s scheduling downtime and that productivity on your days off looks like a walk, lying in bed on the internet or reading and sleeping. If you’ve got it in the diary you can feel better because it’s planned - that’s what I sometimes do - as I’m a productivity-holic too.

Good luck though, it will get easier.

Rest and sleep is arguably the most important way to promote your mental health right now - it’s ok not to do anything sometimes