I have struggled with the mundaneness of life as a parent too
When it feels like same shit.... different day, what I tend to do is take a break from the routine It is so important to allow both yourself and your family to experience the joy of living again, not just paying bills, putting food on the table, keeping a roof over your heads...
Some stuff I have done
Take a day off work and school, take all the kids for a picnic or morning out somewhere kid friendly. Just take water bottles, snacks/sandwiches and buy then cake or icecream and walk and play in a park. Step off the treadmill and stop to smell the roses.
Have a special but relaxed family dinner or afternoon tea. Get the older kids to help, have music playing and dance together while getting it ready, have a giggle, be sillyPut some flowers on the table, have some favourite foods. Make them feel special and give them each a small packet of chips/chocolate bar -but first they need to say one nice thing that they are thankful for that someone at the table did for them in the last week...no matter how small it is ('cept the baby can't speak yet- when old enough they can say "ta" :) Chat with the kids, get to know them again. Have a laugh Listen to how they are and what makes them sad or happy. 3.
Learn something new . Do you want to try a new hobby/exercise? For me I just started weekly meditation & yoga again after 20 years, and it is so relaxing and makes a huge difference to how I feel and facing another week of full time work with 4 kids 10-17. And the kids have a laugh about my chatting about the classes and funny positions I had trouble doing/the sexy yoga teacher (it's not just me, all the younger women & men hug him and fawn over him after class!)
Do whatever you need to do to start feeling sane and like you again, otherwise PND becomes more and more likely Been there and I still struggle at times/ You are definitely not alone xxxooo