Guys, Why did he randomly tell me not to fall for him?

So I've been seeing this guy for a little over a month, we were both quite clear to start that this would be a friends with benefits type of thing because neither of us are looking to be tied down atm. Things have been going well and we text quite often (well sexting more so) we were doing this the other day when he randomly said "be careful not to fall for me" I brushed it off and said that feeling complicate things and I was more interested in the fun without the drama, made a little joke that I should have said the same to him. We carried on texting but he seemed a little colder after that. I'm just confused by the situation, I thought we were on the same page but I'm starting to think he wants more šŸ¤·ā€ā™€ļø any guys shed some light?

Guys, Why did he randomly tell me not to fall for him?
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