Here's how you can tell if the BF is a keeper: does he cut a date short if you are sick and doesn't complain about it? Does he show concern when you are sick and asks if he can get you something for it? If so, then don't worry about being sick around him! If he whines when you're sick or doesn't believe you, ditch him.
My fiance and I don't have long conversations about the condition of my stomach, but I don't have a problem telling him that I don't feel good or that I need to lay down or stay home and that it's because I have diarrhea. Now my mother, I'll tell her all the minute details of my bowel movements, but then she's a nurse and used to such things. Funny enough, my future m-i-l has the same problem as me (no gall bladder) and she and I will get talking about it and get fairly graphic, lol. But even my fiance doesn't have a problem telling me he has diarrhea because he knows I'm the queen of gut medicines and I will surely find something to fix him right up, tell him what foods to avoid to see what's causing it, etc.
You can't marry a person you don't have that kind of relationship with. "...In sickness and in health." Mind you, you have to get worked up to talking about it--not something you bring up a lot the first month of dating, but when he gets comfortable enough to fart around you, then you are free to discuss your bowel disorder on equal terms, lol. And I talk about my problem some to my friends. My closest ones are aware that I have stomach problems. Some of them have it too. Stay on this website a while and you'll lose all shame when it comes to talking about bowel function and you won't have nearly so hard a time admiting it to others in person. If they make fun of you or refuse to even sympathize a little, ditch them; they're not your friends anyways.
Lol, you'll find out I'm the cut-and-dry brutal person on the forum. I'm thinking of hiring myself out as muscle to go with people to see their doctors and bully the doctors into testing and treating them. Maybe I'll start the IBS Mafia. "Test her for bacterial overgrowth or I'll break your kneecaps." LOL.