I hear you. It's normal to feel like this sometimes. Life with small kids and the relentlessness of shift work etc is hard But the way out is to change things and make a plan.
Could you work less days but longer hours in the week? Get some wrap around but then have even a morning in the week where the kids are in school and DH and you have a bit of time together for a walk, catch up, chat?
Can you really focus on Saturdays as family days to give you what you're feeling is missing? A different adventure each week with a walk somewhere new, picnic, museum, activity together?
I would have a real plan for Sundays if they're the real sticking point.
Use your family Saturday to gear up for it if you can. Incorporate a visit to the library for new books to look at on the Sunday maybe, even prep the Sunday food if that's a heartsink thing.
Do you have something regular and free like Junior Parkrun close by? Get into the habit of having to be up, out and at something like that (early swim session - quieter, or family church if that's your thing - they'd welcome you even if it's not!)
Create a tradition of going to a cafe after, or into a charity shop to all choose a book, or into the supermarket to pick up ingredients for baking, or to make something different for lunch. Then head home prepared to get into whatever the thing is.
Invite people round for tea each week, get the kids to bake for them, or have play dates.
Or look into local attractions memberships or passes and agree as a family that you're all happy to have it as a joint gift to each other, and then go regularly - invite others who also have passes if it comes up.
Round us loads of kids activities and sports have training or sessions on a Sunday - switch something regular to then - swimming lessons, climbing, football, hockey, rugby etc. Something they can both do even better, then you can have a breather with a book and cup of tea.
Or make Sundays do some heavy lifting for the rest of the week. Make it your boring day - take the kids food shopping (or plan click and collect), do the cleaning - give the kids simple tasks and move through the house together (or set them up with the TV and/or independent play, change the beds, sorry clothes, do school reading books and other home learning, take the car to the car wash, do a tip run (dh can help prep on the sat), clean out the pets, batch cook and bake ready for an easier week. Might feel like drudge but also a favour to your mid week self?
Make a tradition of Sunday evenings - bubble bath, hair wash, nails etc for kids, sitting room floor picnic in front of the TV, or popcorn with a film, or kitchen disco, or make your own pizza (cheat and use wraps)
You can make this better, it can be less bad. So hard to make changes when you're down and tired but enlist help and strength where you can.