Gosh thats so draining, you poor thing!
You need to get to the bottom of this before you're completely burnt out!
I'm no expert but I am awake so let's see if we can work anything out for now.
So I've got 3dc (2 boys and a girl) and have had some similar issues with each of them in the past.
I'll start with a few questions...
Have you spoken to your HV or G.P about this yet?
Do you know if you have a homestart scheme in your area?
If so ask your HV to sign you up to find a match.
(I hear they will watch the kids while you catch a quick nap, as well as helping you get on with day to day household faff, admin, days out, watching kids during appointments etc)
Does he eat much throughout the day?
How often does he nap in the day and do you think he is getting enough exercise/stimulation?
If he does nap, does he prefer a quiet room or will he sleep through regular household noise?
(1 of mine can only sleep when it's noisy, I used to have to put a story c.d on loop and just let it play most of the night, now he's much older he wears a set of wireless headphones to sleep so we don't all have to hear his noise)
Will he settle himself with a bottle of
breast milk/formula/water.
(I know some would disagree with this but I found that 2 out of 3 of my dc slept better/settled faster and for longer with me giving them a bottle in bed)
Could there be anything else such as teething, reflux etc
Final question and this is a silly one, bear with me!
Does he have a nappy change throughout the night?
That was the trick with my dc3.
As soon as I would whip the nappy off the little monkey would settle and I found it easier to get him back to sleep after.
Hopefully someone a bit more sensible will be here soon to offer some practical advice.
Hoping you can get some sleep OP xx