Your DH's conditions are both autoimmune disorders - and painful; I'm sorry he's having to cope with them @TinaTeaspoons.
A lot of autoimmune diseases start very gently, often around puberty. You have a few glitches, maybe some illnesses that get put down to a virus, hangover, stress or whatever. As time passes, the same cluster of symptoms seem to be occurring more frequently and intensely. You try really hard not to join the dots until it forces you to.
A fair few of his same-age pals will be in that phase now: denial dressed up as "aches & pains, haha, comes to us all" and "yeah, a holiday will see me right". I know I was putting all my faith in a tougher exercise regime (which was actually making me worse, but I wasn't looking at the dots!)
The UK Crohn's & Colitis UK charity reports at least 1 in every 227 people in the UK has been diagnosed with ulcerative colitis. The majority seek diagnosis before the age of 25, so he did actually get a late start with that one. Small comfort, but still.
I'm not that keen on being the misery who loves company, but I really understand how he feels like the unlucky one. He is, but it's also true that more of his friends will be stumbling than he knows.