Complete mystery

I've been with my boyfriend for 2 years. He's very affectionate with me & he doesn't cheat on me. We practically live together. We have a lot of fun together.  But, there's one thing I can't get past. He will never be serious. He will always find a way to turn a serious conversation into a complete joke. He never wants to talk about anything real. He doesn't talk about his feelings at all unless he needs to blame me for something.  He needs to find a way to make me laugh so we can change the subject. When I persist on staying on topic, he gets angry and ignores me. And he has never once told me he loves me in 2 years. I'm sure he loves me, because some things you just know. But, it's the fact that he has never said it. He did the same thing again last night when I tried to talk to him. He just lay down and turned his back to me repeating over and over again that he doesn't want to talk about anything. After a while, he completely ignored me until he fell asleep. It makes me very angry when he does it. I tell him that, but I don't think he grasps how angry. By the way, he's 30 & I'm 28.