If income is low in relation to the number of people and needs, then things will be a struggle.
I think there are 2 categories of people who have a struggle pretty much every month. There are those whose income is just exceedingly low and insufficient however carefully they budget. Even when they don't have the heating on or consider replacing things like pillows (because the thought of having £5 spare to spend is just beyond their budget to even consider it) by the end of the month or week they are still struggling to buy the most basic food or hygiene products or pay for their energy or rent. If they are choosing between food or heat and haven't bought other stuff, income is just simply insufficient and all kinds of careful budgeting whilst helping won't remove that poverty.
There is also the situation of struggling due to poor budgeting and judgements about what needs to be bought. Lots of people have a reasonable if not high income and really struggle. As said, one off expenses come along every month - they might differ each month and one month be shoes and the next be a Hoover, but you can guarantee there will be something and so because of this they have to be built in as regular expenditure. An amount has to be allowed for those which are essential expenditure before money is given to other luxuries.
So Op, would it help to come up with a figure for these monthly expenditures which always crop up and incorporate them in into your budget. It might mean you have to take something else out or save somewhere - can you have a cheaper phone or save on utility bills or go without a holiday or cut out some luxuries like takeaways? This might sound dull and a bit miserable, but if you have £X in the budget each month for necessary miscellaneous expenditure then you won't have this stress every month. Do it this way round with the budgeted money being for necessaries and left overs for luxuries, not luxuries coming out first before the necessary one-offs which as you say, always occur.
And then it also helps to develop an attitude that as you get to the end of the month, everything doesn't need spending. So if you find there is £100 left, that doesn't t mean buy another takeaway or look round for what you might replace, when the existing things are perfectly good, but keep that money and build up a reserve. Perhaps if you put £200 in your budget for miscellaneous necessitates and it comes to the end of the month you could have a policy that if there is still more than £150 in that account, you can spend any excess over £150 but won't spend further into it? Would that help?
Looking really closely at budget helps a lot. Therecarevloadsnof threads on MN where people cut the cost of their food shop by looking at it closely. Working out where the money goes really helps. Lots of people spend a big chunk on takeaways or on nights out or on clothes or make-up or a hobby or on regularly replacing household items which they fancy a new one of, but which the existing ones whilst not perhaps the latest version are fine. This is often the case with clothing and shoes. It is partly about a mindset and about making things last a bit longer and not thinking new is always needed - so yes to bleaching the sheets or getting the carpet cleaned rather than replaced and to just keeping the storage unit you don't like rather than lusting after a new one because you saw one you liked. Of course things that break might not be repairable and need replacing like shoes or washing machines perhaps, but today we often do replace when we don't need to and could think about that a bit more as a way to save money.
Children's attitude to money can also be a real drain as hey get older. If your kids develop the idea that their worth and value is in the labels they wear or the amount if new shoes they have, they probably will pester you and make you feel like you're selling them short by saying no and your own worth starts to be related to the material stuff you provide for them. I know it's hard if you're very hard up, but working on their attitudes to stuff helps. Valuing doing well at school or being kind or developing a hobby or skill means the trainers you wear cease to be so important.
If income is low, getting into that position where you can build into the monthly budget an amount for the unavoidable one-offs and then building up the surplus that allows you to sleep at night is hard. Quite how hard really depends on your income, but many people can get into A much stronger position if they really want to. Visit someone like a debt or budget organiser (free) who will non-judgementally look at your budget with you and help you reshape it. Often the reason people struggle is because of debt repayments being outbid control - the advisers can help sort that out too which brings massive relief for lots of people.
I'd say, it's easy to mason and do nothing and find yourself in the same position every month. It probably sounds preachy but actually taking some action can turn things round and make a massive difference and make your whole life better. Money worries grind people down and suck the joy out of life and there's nothing like seeing someone feel unburdened in this area, often with some fairly simple changes.
Op, would you be willing to go and see someone to see if there are any adjustments you could make which might just remove this horrible monthly feeling? Other people too who feel trapped in the same way, it might be possible for you too.