My arsehole ExP does exactly this, like it was a competitive sport. And every single time, he would state that although he had said this before, this time he actually did feel like he was dying/his organs were failing/this was the most ill he had ever ever been, etc.
He turned a common cold into 4-5 days in bed watching Netflix and catching up on sleep, while I struggled on with 2 kids getting more and more knackered - to the point where I got severely anaemic and B12 deficient and 1/2 my hair fell out in great handfuls everywhere. A stomach bug just last week sent him to bed for a week (he still lodges in my front room as he is 'saving up a deposit' to move out - it's been 6 months!). DS1 and I had it too, DS had 2 days off school as a precaution but I just had to dose myself with immodium and get on with it all. Ex refuses to take any medication for anything as it will 'make him worse'.
All his illnesses were carefully timed to coincide with birthdays, Christmas (he went back to bed as ill before kids even finished opening presents several years), days out...
ExP doesnt take me being ill seriously at all - if I am not bedbound, I am clearly not ill, even if I point out that bedbound is not an option for someone parenting 2 kids including a BF baby basically on their own. He seems to almost get angry with me when I have been really, undeniably ill. When I was admitted to hospital he was a total arsehole, and went out on the piss an hour after I got discharged.
Sorry for ranting, I think you touched a nerve!