Going off sick won’t help if you just have a few weeks off then go back to the same routine.
Going off sick to prevent burnout and establish a new routine/ re-establish order is ok if it’s what you need to protect your mental health.
Think about what you need to change to make things easier/ better for you. I’ve listed some suggestions, only you and DH will know what will be best for your family/ finances etc. obviously none of Theresa will be the answer alone but may give you something to think about about.
Remember, if you need to go off sick to protect your mental health, that is ok. You don’t need to feel guilty or worry about your colleagues as mentioned up thread. That is for your/ their line manager to consider.
Reducing hours, compressing hours, switching to a childminder, using a nanny, nursery in diffrent location, hiring a cleaner, meal delivery service, using a laundry service, preparing the nursery bag for the whole week rather then each day, giving yourself more time in the mornings to not feel rushed, DD having breakfast at nursery if an option, same for nursery lunch.