Why not try this for a simple meal plan this week:
Mon- jacket potatoes with whatever toppings you like- tuna/cheese/beans
Tues- spaghetti bolognese. Start with a dolmio jar until you feel more confident cooking.
wed- sausages and mash. Buy big bag of potatoes. Will go much further than ready made mash, plus can use for other days’ dinners.
Thurs- veggie or beef burgers with homemade chips and salad
Fri- chicken stir fry. Chicken breast, pre-made stir fry veg and sauce with rice
Sat- takeaway
Sun- whole roast chicken, veg, roast potatoes
Could you try swapping Diet Coke for sparkling water? Get the same “fizz” on your tongue, but none of the sweeteners and nasties.
Not sure why you won’t do online shopping, but I do it, and it stops impulse purchases.