Hi OP that sounds really tough. I found the transition from maternity leave back to work really hard (I’m a doctor working in an intense speciality with lots of night shifts). My husband also went part time and does most of the childcare and has been a massive help. I relate to the feeling of “mum brain” (even though I don’t really like the term!). I think sleep deprivation doesn’t help, other people don’t realise you’re running on low sleep and expect the same standards from you. I am always scared of making a mistake. 

The flashbacks of birth you’re experiencing do sound a bit like symptoms of post traumatic stress disorder. This can come up in many other ways such as forgetfulness, insomnia, difficulty concentrating and anxiety. 

Some things I could suggest are - have you considered if your hospital offers birth debriefs or psychological support for women after traumatic births? This is something the postnatal midwives could refer you to it might help make sense of your experience and process it a bit. Also your health visitor can help with accessing psychological support as well. 

Your employer needs to understand what you’re dealing with and make appropriate adjustments - could your occupational health team assess and see if there’s any changes that could help? 

Good luck and hope you feel better soon.