Sarah,
As people have pointed out already, everybody handles their emotions differently. People also handle their diabetes differently. Most people I know know that I an diabetic. I haven't always told these people straightaway - the people who need to know do know.
Maybe he doesn't like talking about it mug. I used to be the same as far too many people don't understand diabetes, particularly type 1 (in my opinion, anyway). Could be another reason why he is keeping thugs from you, though.
I don't think you are going to get the answer you're looking for on this forum. Bite the bullet and talk to him. Find out where you stand.