Morning OP. Just realised my post was only sharing in your misery and not offering any helpful advice. Apologies for typing in a rush (3 kids under 5 so all hands on deck a lot of the time!).
One of the things that is difficult is just having one child. I'm in no way suggesting the answer is to have another child, just sharing an observation that friends of mine who only have one or who have bigger age gaps than me so only had one child when their eldest was your sons age found it HARD work. They want to play with you all the time! Mine rarely ask to play with me as they have each other to fight play with 😂 which both occupies them and wears them out! Appreciate there isn't anything that can be done about it but it does help to keep perspective. I know when I only had one I used thinking fml I find this so hard how does anyone have more than one?!! And the truth of that is some bits are harder with more than one child and some bits are easier.
The answer definitely lies in getting out of the house and doing as much interesting stuff as you can think of. Museums (some are excellent and very interactive for children), farms, play parks, role play cafes, soft play, splash park, literally anywhere you can think of. A ride on the bus or train. We have NT membership which means somewhere new with open space to run around and hopefully a nice bit of cake in the cafe. A few "big" days out a year to the theme park or zoo or similar. They love going to things like our village fete or country shows where you can see the animals and there's lots of tractors to look at.
Persist in going to the church hall type toddler groups. Find one you like with a few mums you enjoy chatting to. Even if DS clings to you, he won't forever. The more you go, the more confident he will be. At this age children mostly play alongside each other but in a few months they will start doing some simple cooperative play together and that will be the point where he will branch out and you will get to drink your coffee!
At home, just having one or two boxes of toys out helps. I periodically tidy up when I notice they're not playing with it anymore or at certain key points of the day (before we go out, before nap time, before dinner). Seems to refresh their interest in it if I pick it all up again. Having some fun garden toys helps too. Sandpit, water table, paddling pool at this time of year.
Don't be afraid to let him watch a bit of tv if you just need a bit of a break. Mine watch way more tv than usual when I'm pregnant and struggling. Stick CBeebies on and breathe. Loads of educational stuff on CBeebies. But mine also love tractor ted and a monthly subscription to that has bought me hours of peace!
Setting up a few simple activities once or twice a week and baking together once a week helps me feel like I'm offering them some chances to learn and be creative. We also read lots of books, I practice reading with my eldest and my middle is busy learning his letters and numbers at the moment. My youngest will soon be able to start learning colours etc. thinking of fun ways to teach them things can be really rewarding. My eldest loves cars for example so we used to practice looking at the number plates of cars we saw and seeing if he could recognise any of the letters or numbers.
If you can invest in a balance bike and a little three wheel scooter for him. My middle one is a whirlwind of physical energy and he was excellent on both of these by 2.5. Wears him out well!! My eldest is now confidently peddling having come straight from a balance bike and skipped stabilisers. Hoping to do the same with my middle one soon, so more opportunities to tire him out haha!
Don't bother going food shopping. Get it delivered or in our house, it's now my DH job on his way home from work. Amazon prime any random things you need to save the stress of shops.
Take reins and the pushchair everywhere. If he runs off, he has to be contained in some way. Even if he screams or thrashes. If he behaves like that you can always leave. Mine have soon learned if they mess me around by running off they will be back in the pram and if they don't listen to me I will just go home. Didn't take them long to get the idea haha.
Be well prepared with easy to eat, low mess snacks for tricky moments. Mine know that once we're back in the pram and ready to leave the park it will be snack time. Makes going much less painful! Eating outside as much as you can. Snacks in the garden this time of year, picnic in the park on the way home from wherever you've been. Less mess to clean up at home.
Most importantly, make some mum friends with other children roughly the same age. Yep, you won't ever get a full sentence out to each other but it's far more enjoyable doing things together. The days are long and lonely otherwise.
Hang in there OP. My eldest was such bloody hard work as a toddler and he is a delight now. My youngest is still little and lovely and hasn't yet hit this stage 🫣. My middle one is thick in the seriously hard work toddler years. This time though I know it's just his age and in time it will all improve! No doubt in a year or so my youngest will be a nightmare. I used to think I must have done something seriously wrong for them to be such hard work, now I know that they're all hard work at this age.