Friends with benefits & Friendship circles

I'm Kelly, 19

I really need to figure something out...

So I've been doing this friends with benefits thing for a little while, but like we've only seen each other twice. First time we agreed it'll be kept low key, which I was cool with, but then he went and told his best friend, which i knew he would and I was chilled with, but then his best mate started saying things about it to me around our other mutual friends, when this guy (C) wasn't there, and he put me in an awkward situation everytime where I had to kinda explain myself to our other friends.

Then C said he needed to talk to me, and when he did he was just like, "I know you told everyone" so I explained myself and then we were chilled, but he said that the reason he wanted it to be low key was because someone else (who he wouldnt tell me the name of) has a crush on me and he doesnt want it to be rubbed in this guy's face all the time, so I left it.

Then I had an idea of who it might be, so I asked one of our mutual girl friends if she knew anything about this mystery guy and she said no, and left it there, but I think she told C because now he just sent me a message saying "You are ridiculous" and I don't know what it means... and I don't know how to handle it

Thing is I'd normally put up a fight, but I'm not extremely close with the other people in our group, while he's best friends with the "ring leader" and I feel like if I defend myself, the rest of the group will exclude me like they did to this other chick.

And it's not like I can just switch groups cause the class I'm in at University is pretty small and they really are the only kind of people I'd like to associate with.

Damn I sound like a middle schooler,

But Please let me know what you think asap!!

Best wishes