What is "crossing the line" in a friends with benefits relationship?

[Anonymous]

I know what friends with benefits is, or at least should be. Recently I've noticed my best friend of 5 years, but recent friends with benefits, has been acting weird. We've discussed being in a monogamous relationship before, but he doesn't want to commit (he didn't say that exactly, but that's what I got from our convo). Yet he acts like we're together. He pays for stuff sometimes, takes me places, always wants to see me, calls/texts everyday and he even questioned a guy who was texting me the other day. I want to be in a relationship with him, but until then I'm free to do what I please. What are some boundaries I can set with him, without offending him or hurting his feelings?

[jacquesvol]

That depends on which lines both agreed on.

[Asker]

We didn't agree on anything, it just kind of happened and we both went with it.

[jacquesvol]

He acts like you're together.
Time to have a talk about it indeed. What boundaries do you want to set? Exclusivity? Or advance warning?