It sounds like your budget is very vague and you're not sticking to it in its vague form!
You need a fixed budget that you stick to like glue. It can be as detailed or not as you like. Some people budget down to the penny and the individual expense. You don't have to do that if it doesn't work for you.
So your household bills inc mortgage are £3800 pm
(does this include one off yearly expenses divided by 12 because it needs to? Eg house insurance, car insurance, car service, mot, TV licence)
Phone your providers and negotiate your bills down. Threatening to leave subscriptions often gets you a discount. Shop around for everything
Your food bill is £1000 pm
(is this all your food? Any top up shops? Takeaway? Eating out?)
This is very high. You can easily claw back hundreds a month here if you meal plan, batch cook, buy less processed food, eat leftovers etc
But at this point you need a mindset change. The rest of the money at this point is not each of yours to spend as you wish!!
Next you save something - how much per month? For what?
You need to save for short term costs like christmas, DC birthdays, Christmas, holidays
You also need to save for the long term
After that, then then you need a budget for joint costs eg DC dinner money, school uniform, school trips, DC clubs, house maintenance, family days out etc
Then whatever is left is yours and DHs to spend as you like on coffeees, lunches, haircuts, clothes etc