Start by sitting down quietly with no distractions at all.
Set your phone aside.
Close your eyes and visualise the sort of peacefulness you want to achieve.
Then picture yourself walking through each room. You are happy to see there is a place for everything, windows are open, a breeze blows through, and you know that all is airy and fresh.
Hold onto all of that.
Start with your kitchen.
Take every single thing out of your cupboards and pantry and throw out everything that is out of date, chipped, cracked, wonky, broken, plastic storage without lids. Do the same with drawers and under the sink. Hoover drawers and cupboards and wipe down with white vinegar and a microfiber cloth. Put back what you're keeping. Take the junk out to the bin immediately.
Move on to the fridge and freezer and throw out everything out of date, anything whiffy, anything you can't immediately identify from the freezer. Wipe down the interior and put back what you're keeping. Throw away the rest immediately.
Make a list of items you need to replace- food, plastic storage, etc.
You'll feel organized and on top of things when your kitchen is done.
Move on to the bathroom. Get rid of toiletries you bought more than a year ago, any old, ratty towels, ends of soap, old toothbrushes, bottles of this and that with less than an inch of contents in them, and old medicines you have sitting there. Clean your hairbrushes. Clean and mop bathroom surfaces. If you have room for a candle, put one in there.
Do you have an airing cupboard?
Go through the contents. Keep two sets of sheets for each bed.
Do your bedroom.
Take every drawer out one by one and go through the contents. If you find clothes you haven't worn in the past year, get rid. You can throw out or donate. Do the same for wardrobes. Your goal should be to get rid of two thirds of what you currently have. Pull everything out from under your bed. Make decisions. Get rid of all but two sets of sheets and pillowslips, one on your bed, one spare.
Shoes with holes, scratched or down at heel boots, smelly trainers, heels that give you blisters - make decisions. Keep only what makes you feel comfortable.
Immediately after you've made your decisions, the discards have to leave the house. Then hoover and polish, turn your mattress, put your sheets in the washing machine.
Then on to sitting room and dining room. You probably know what needs to be done there, followed by immediate removal and a deep clean.
If your child will be in school all day there will be a good few toys that won't be played with much. I would invest in a big box (or even a big cardboard box) and put all sorts of small toys you consider junk into it (happy meal toys, souvenirs, stuff DC doesn't play with much) If those toys don't get asked for or looked for or taken out for two months I would quietly throw them out. Mark a date in your calendar.
I would keep half a dozen favourite stuffed animals out and put the rest in another box. Keep toys that facilitate writing, coloring, painting, building, creativity. Keep books, even baby board books. Children often cut their reading teeth on familiar books.
Do you need all the coats, jackets, gloves, hats, scarves, and mittens you may have? See what winter brings and discard in the spring.
Clothes your child has grown out of and summer clothes that won't be worn again - discard/donate. Footwear - same.
If you find yourself dithering and indecisive and losing your motivation, go back to your mental picture of the breeze blowing through a room you are happy in.