Fiance troubles

Lately my fiance has been coming home from work pissed at the world and I can't seem to get him to talk to me. He instantly snaps at me if I ask what's wrong and he tries making me feel bad about trying to make sure he's OK.. I'm getting so fed up with it it stresses me out to where I get shaky and queasy and just want him gone sometimes. Then the next day he will act like nothing was ever wrong and it confuses me to death. We have been together for two n half years now.. I had to vent.. Have no one to talk to