how to remove my bf form 'comfort zone'

we've been dating for the past two years now and things where hot and happening until now when I got into thinking that maybe he is no longer interested on me, I think my boyfriend is at "comfort zone' and when I ask him about how he feels right now he yells or just remain silent and another problem is that he is not really an outspoken person..how will i know the real problem but i think he is enough now.......advice plz