Hi,
I sympathise. I was in exactly that place about 16-18 months ago. I started by doing 5 minute You Tube fitness videos every day. I bought some cheap clothes that fitted properly (M&S jeans, Shein floaty dresses).
Make small changes that have instant impact - 5 minute HIIT or yoga videos or a really easy longer workout like the Leslie Sansome walking ones are perfectly doable in the kitchen while you cook or before DC get up/after they go to bed.
Do some easy self care: drink 2l water a day. Keep track of your 5 a day and increase it to 8 a day. Make a list of your favourite food that happens to be healthy too - eg berries, natural yoghurt, cherry tomatoes with fresh herbs, fruit or herb teas, good fresh roast coffee, roast salmon or chicken breast etc and start building menus around these. Start thinking of healthy treats.
Don't diet but do use My Fitness Plan.
Do one major self- care thing each week - hairdfresser, manicure, peducre, facial (most can be done at home for bery little money but do get a good hair cut) eye test, dental check up with hygienist etc.
Reward every step along the way with non-food gtreats: new nail polish, a face mask, body massager, moisturiser,Epsom salts, fresh flowers, scented candles, a magazine or novel etc. When you are tired, angry, upset, put upon, overworked and undervalued, go to these treats to self soothe.
Buy a couple of very fashionable things you really like and a couple of staples.
Get some well fitting, comfortable trainers and fitness gear and get into the habit of wearing it for your at home workouts.
I didn't diet but lost a stone and my confidence is so much higher. Still have one and a half stone to go, but it's a good start