He frustrates me to no end....

Whenever I have something bothering me about our relationship and want to talk it out, my Bf gets silent. Occasionally I can get him to say something but not tonight. We've only had 2 fights in 2 years. I just want to talk and see if we can rectify the situation calmly. Grrrr...why does he do this? I love him more than anything but I'm so frustrated.