I feel for you, My DH, does have real back pain, there is no doubt, he has had all the X-rays/etc, etc but the moaning drives me mental. I treat it like white noise now , & throw in, "I am not a doctor".
He is capable of enjoying himself, he can work, physically, unbelievably hard... BUT, he has to moan.
It is attention seeking, & is something his parents both do.
Every hour, involves a possibility of attention seeking, by a complaint.
In your shoes, I would say:
"I don't believe these pains, I have yet to see you consult a doctor, I am not your mother, & will not be running with a cloth to cool your brow. Either there is something wrong, or it's a attention seeking bollocks.
I am NOT living this way any more. It is like a crying child, women are tuned in to hearing, a cry = "alert, my child needs help" but you don't need help or you would seek it out. Your behaviour is a total turn off, it is pointless, tiring, depressing & I will not be manipulated.
I do NOT want to hear it (even if it was real, I wouldn't want a detailed documentation of every pain) or have a text mentioning your half baked attention seeking drama.
Either you stop or see a doctor & discover if you do have a real problem. or you move out."
(to be honest, he probably doesn't even know he does it half the time, its become a habit, like breathing )