Hia,
I’m not a specialist or anything but I would like to think how your feeling is a normal emotion for what is currently happening. Change can be daunting but you and your partner have both decided it is for the best going forward. You know you were happy in those times as your looking around and can see good memories (most bad memories don’t go the walls) and the future is uncertain so it brings a sense of sadness that this current time is ending.
If anything you feeling sad now is a testament to the good times you did have and will miss. If you stay as friends which is recommend being your daughter’s father, then it doesn’t mean you can’t have my happy memories in the future.
I have been in a similar situation, my fiancee decided it was time to end our relationship right after my birthday in February just gone, then covid happened and everything got complicated. It took her a month to move out. We have a daughter together who is 7. Her mum took a matter of weeks before telling me she was in a new relationship so it was serious and now… Anyway that’s a different story. Basically I hope my ex felt some form of sadness when she ended things. I still don’t free that the love had ended but if love can’t be one sided and I’m devastated every day.
You may feel some sadness now but that’s normal. When your new routine and life begins again you will have new happy memories 🙂