Today's the day. I'm gonna find out why he's so distant. Any advice?

It's been going on too long and I've had my head in the sand for too long. Today, we're both off work, and I damn well want to know why he's been so distant for so long. Why he placates me and and is never interested in . If he's cheating. And generally wtf has been going on. Any advice on how to plow through this and stay on course and not be waltzed around by his tactics?