I do say (nicely I hope) that sometimes mummy needs him to be quiet but its like he has to tell me every single thing that's in his head at all times
He is at such a difficult age. Still not quite at the point where he fully appreciates that you and he are separate human beings and that you have your own thoughts and the need to finish them and focus on your own work, but at the same time fully verbal, and inclined to go on and on about stuff that is only significant to him, and repeat interactive games until you are tearing your hair out and climbing the walls. Playing by himself for long stretches may be a challenge. Children around this age with siblings often spend a lot of time squabbling and fighting. It's tough.
Don't worry about snapping at him, @Saylethewayles.
You are allowed to state your needs forcefully every so often. You reconnected afterwards, and hopefully he came away reassured that all is ok.
Any mother who says she's never yelled at her child has to be a liar IMO. Or a robot!
That constant stream of consciousness, verbalising every single thought can drive you batty.
We've all had that moment when your head explodes and you find yourself snapping/shouting.
YYY to that.
Don't set unrealistic standards for yourself, OP.
Try to state your needs consistently though, as it will benefit you all if he gets to the point where he can play independently and develop his ability to concentrate on an activity.
Give him a pep talk about people needing their own space as well as the feeling of connection, and maybe try to establish a set routine to his days so that you can rely on some quiet time when you don't feel so bombarded. He won't feel rejected if you ask him not to follow you around, probably more relieved that you have organised his whereabouts for him. For instance, tell him you're going to have a cup of tea in the kitchen and you would like him to stay in the sitting room and draw pictures of zoo animals while you have it. Thank him for staying put.
Could you and your H find some age appropriate interactive learning sites he might enjoy, that would keep him occupied for a stretch of about two hours (with breaks) in the morning and another two hours in the afternoon? Try to get out for another set amount of time.
It is important that your H, regardless of his job and its demands, takes part in the daily parenting. Being a partner isn't only about providing an income, and don't fall into the trap of believing that bringing home the bacon absolves him of the requirement to support you as his co-parent and as his partner. You need daily uninterrupted time that is completely 'off duty' to spend a while inside your own head.
Try to set a little time each weekend for actual time off for you.
Try to do week-long or even two week-long meal plans too - the burden of deciding what's for dinner every day, then cooking it and clearing up afterwards sucks the joy right out of life.
I think counseling would be a good idea, but your sleeping problems may indicate you need to see your GP. Melatonin might offer a solution, or anti-anxiety meds.