How to get a guy to open up?

What are some ways for me to get my man to open up about what's going on? He's been very irritable for the past week, talking mean to me kind of and being snappy. I try to talk to him cause I'm not crazy, I can tell something is bothering him and he just gets mad. It's making me feel like he don't care for me anymore, either, but when I ask he will just say he don't wanna talk about our relationship. We have been doing good in our relationship but the past week hasn't been that great cause of the crap on his mind. Anyway, any help would be appreciative. Thx!