Relationship help?

My boyfriend and I have only been dating for about 6 month now, and I feel like everything is just fizzling away. He doesn’t seem interested when we talk and is very calm when we hang out. It use to be where we had hours of convos and it was so fun to hang out! He has never been really one that flirts with me, but he is very sweet and a has a great family. How do I bring up the situation? Are we just fading away?