It's easy to feel overwhelmed as a mum op. I have been there myself. It's nothing you are doing it's just life with dc can get that way sometimes and it's hard to get out of it. I think the reason it gets like this is mostly our own expectations and always aiming for a better time, eg..if I just get to Xmas things will slow down, if we just get new carpets and do more of the home improvements things will be better, when dc is in full time school life will be better. You get the picture. Thinking like this can make life feel very much like a chore in every way and make the present seem like something to get through and endure.
It's possible to make life easier and more enjoyable. I will never let myself forget to live and just get through the days like a drudge or let life be purely work again, because doing that led me to misery and mental health problems. I was just trying to make everything 'just right' that I forget to live and felt as you describe. Some things won't be doable or relevant to you but things that I do are
I have changed jobs a few times to find a good fit and I studied for a job/promotion that means I work incredibly flexibly and can work part time and still earn well. That's not always possible but could you condense your hours to give you a day off during the week? I have two days during school hours that I'm not working, I do work longer hours on other days but it means on the two weekdays I can get on top of chores and dc admin and take some time for myself. It frees up evenings and makes life more organised. Because it's every week eventually getting on top of stuff becomes less needed so more time to yourself. I sometimes go back to bed or il go walking or to meet friends. Sometimes I just sit and switch off. It's life changing. My colleague was on the verge of a breakdown and has reduced her hours so she has an extra day a week off and it's improved her life so much. She says due to tax it actually doesn't make her massively worse off. Work recognised it was this or she left and are pretty accommodating if it benefits everyone.
If that's not possible I'd look at doing short bursts of chores so weekends are fairly free so you can take a chunk of time for yourself.
I have hobbies that I can share with my dc so that time with them is enjoyable for all and feels like it's more for me too. This can help you feel less like you do everything for everyone else and nothing for yourself.
Who sends your dc money and what is it for? If it's regular from a relative for example can you use some of that money for family things such as days out or home improvement rather than them just buying stuff. This will help with decluttering and improve things for the whole family. One of my dc gets regular money, mostly it's used directly on her but sometimes I use it for days out or even for myself or something for the house because it's to benefit her life and these things do benefit her indirectly. If it's not regular money and just pocket money from you then id cut back and also only give it every so often and on the condition that they contribute to the chores and running of the home. This will stop them frittering it on crap every week, that you then have to send back, and give them incentive to do more taking the burden off you.
Can you cut back on anything at all to afford an occasional cleaner? I have one every two weeks but even every month would be fine. She is very through so it's less time consuming when I do top up cleans in between. If money is too tight fair enough. One thing that you have to do is massively lower your standards and then lower them again. I have the privilege to go in numerous homes and a very high number of them have blemishes and imperfections and are not as tidy or clean as many people seem to think houses need to be. It doesn't harm anyone unless it's squalid. Toys all over the place, full sink, bit of dust, a few bits on the carpet, unmade beds etc are all normal and fine. You will free up lots of time and feel less overwhelmed if you let your house be a bit more messy.
Reduce the dc clubs or look for similar on nights that are better or when your dh is available. I have tried various combinations of clubs so that we are all getting the most downtime and so most clubs fall on days when I'm not already busy. It means that a few nights a week we can come home and have an easy dinner and then chill.
The fun weekend thing can be at home and easier. Your dc are older than mine but even so they would probably enjoy movie afternoons or craft afternoons. Doesn't have to cost lots and means you can also get downtime and break off to either do something else or have a nap.
Make friends properly with parents in your area. We now have real friends who we met through dc who will likely be lifelong. Although it may seem like something else to do when you already feel overwhelmed, it means you can rely on them to help out, for eg take dc to a club. It also means you can have time to relax and enjoy something but your dc can be there. We go on holiday with another 4 families from school twice a year (camping if money is an issue), we regularly go for dinner and drinks with other families and we will go out with the adults separately. It makes life less about the mundane and means that even in the middle of the tough years we have something that is fun for us all and to look forward to. We have no childcare or family support so this way we get to do adult stuff but with the kids in tow. This is not about adding stuff to your already full plate but about breaking the cycle of work and chores and no fun because that in my experience leads to overwhelm and poor mental health. If you enjoy aspects of your week you feel more able to let stuff go.
Put more of the mental load on to your dh. I got a new phone and didn't re download the school apps so now dh is the only one that has them and so he deals with all that. We have a shared online calendar and we both update it and can send each other a notification if it's something the other needs to know about.
Mute all the group chats, work, schools and personal. Only check them when you can be bothered and just skim read them. Most of the stuff on there will be irrelevant to you but them pinging all day feels like there is so much you need to read and do. I bet you won't miss anything important. We coped without constant contact in the past and managed to live just fine.
If there are little errands to run I often send dh a message for him to do it on his way home from work. It's easier to nip somewhere when your already out than make a special trip. It shares the physical aspects of family life. I forgot my lunch today so nipped into Lidl on route to my next appointment and in the middle aisle was a few cheap toys and games. We have a few of dc friends birthday parties coming up so I grabbed a few and will wrap them later. It means I can forget about it and don't have to rush out the day before. I was just mooching about down the middle aisle so it doesn't have to be another chore as such. Plus the items were only £3 and look really good. Dh will do similar and manages all of dc dressing up days and club payments/outfits and all car and home insurance, repairs and payments so I can forget about them. We don't have to actively split the load now which can feel like another burden on you, we have played to each other's strengths, I'm better at the emotional stuff and direct care eg remembering to get dc to the dentist where as he is better at payments and organising returns etc.
Divide up practical stuff fairly. I was at one point doing all mornings and evenings due to different working hours and him walking the dog, but now he does mornings by getting the dc up, dressed and gives them breakfast and does pack lunches before he leaves. I then only have to take them to school. Dh also does all cooking, shopping and half the dc baths and bedtimes. It means we each have evenings where we can relax alone and means that I get to lie in a bit longer in the morning when I have a longer day ahead. Dh works full time but recognises my job is very stressful and I have the better earning potential so we try give each other a break and again work to our strengths. I'm a night person and him morning so we each run our dc and home when we are at our best.
Often accepting that you can't do everything in one day helps. I used to be of the mindset that if I got everything done today, tomorrow I could rest and life would be less full, but the list was endless and it just leads to burnout. You have to to rest when your mind and body tell you to. Acceptance is key, a lot of the time you are fighting against the overwhelm and mundane but accepting this is life sometimes does make it a bit easier to let go.