My youngest two are 13 months apart so I had three children under the age of 4, in an area where children didn’t start school until after their 5th birthday - and no free nursery places at the time!
I managed as a SAHM with a husband who worked away for two weeks each month! I had to be very organised and got all three to nap at the same time each afternoon so I could do the washing and get tea ready. All of them were good sleepers, in their cots in own rooms from about 6 weeks old, only one or two night feeds. I used to bulk freeze sandwiches and snacks so I could breast feed baby and supervise toddler eating finger food in high chair while older child ate at kitchen table. I have no recollection of what or when I and my husband ate!
I used a fantastic silver cross pram to get around, baby inside, toddler on seat on top and four year old sitting in the shopping trolly when he got tired! I used a VW Campervan as my car so could get my pram in without folding it up using straps to secure it! I managed to buy an amazing Mamas and Papas double buggy second hand which had just one seat with two straps which converted into a very comfortable play pen/cot for the baby while we were at toddler group.
I even moved house over 200 miles away when the baby was five months old and somehow managed to cope when he caught meningitis and spent three weeks in isolation in intensive care - my mum drove over 100 miles to live in our house with the other children while I stayed in hospital, she even unpacked all our boxes before we came out!
I guess what I am saying is that you will manage, somehow! Plan ahead, be organised and find out ways to cope, it does not matter if the house is messy or if you only eat junk food, it will only be for a few months! My youngest two are now best friends, almost like twins, and remain very close as adults.
On the other hand, I have almost no memories of that first year!