<human>: Can you condense the text into three sentences or less?

So.....I've been seeing this guy since the early spring, and we've established that we are only friends with benefits. We have sex, we get dinner, and go our separate ways for the night. Pretty standard. 

However, there's been a huge shift in how he's been acting. He used to be pretty nonchalant, but now he randomly messages me saying things like, "I think about you all the time" and "I am really, really happy you're in my life. Seriously." 

We had a conversation the other day about exclusivity, and we both mentioned that we are fine with the other person sleeping with people as long as we are honest about it. Since then, the comments have increased tenfold. He's constantly complimenting me and telling me how phenomenal I am all of a sudden. I'm so confused. What is happening?
<bot>: FWB and I agreed we don't have to be exclusive, conversation went swimmingly but suddenly there's a huge and unexpected shift in his behavior.