Friend with Benefits acting different?

I don't know what's happening. My friends with benefits and I have developed feelings a while ago. I know we weren't supposed to but it happened. It was just incredible time for both of us! We would flirt and tell each other how much we were crazy about each other. The whole thing with love songs and texts.
Then all of a sudden he starts acting different. I am not saying uninterested. It's more like comfortable and less intense, less intimate.
We don't flirt on the phone anymore and he doesn't send me sexy messages. Instead we talk more about work, personal plans and goals, etc.
On the flip side, we see each other more often than before and when we do, it's still sweet and sexy. He stopped saying how much he's crazy about me but his actions show that he can't stay away from me. He even told me he's addicted to me.
What happened here? I'm confused.
Friend with Benefits acting different?
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