City is way too small

We were waiting in the will call line for City Arts and Lectures, my boyfriend of now two months telling me about the restaurant he's taking me to for my birthday next month but won't tell me the name of, and I'm asking whether I should dress up, and could I wear the dress I'm wearing, something stupid, and we're being obnoxiously affectionate, when I hear my name from behind me.

Right behind us in line is my ex-boyfriend, who I haven't seen since the day we broke up, and spoke up right then either because he just realized it was me when he recognized my loud voice talking about wearing my dress to a friend's holiday party, or because he didn't want to watch him put his hand on my hip anymore.

The poor guy looks really uncomfortable, and I default to overly enthusiastic -

"HI! How ARE you!" and introduce them, as they eye each other carefully. He's by himself, so I start to worry that he's attending this event by himself and seeing me on a date, which is beyond uncomfortable, so I ask,
"Are you...meeting anyone here?"
"Yeah, I'm meeting this girl who I've been...dating...for a while... We should have lunch sometime..."
"Definitely! ... Wow, it's so funny to run into you here."
"Yeah, awkward."
"Eh, it's not so bad."
"Uh, I'm going to go to the back of the line..."
"It's fiiiiiiine," I say, to which he smiles uncomfortably and again says,
"I'm going to go...back there..."

I tell my boyfriend I am really curious to see who my former boyfriend is dating, and try to glance back but can't get a look. I tell him I bet she's blonde, with big boobs, and laugh out loud.
He gets a look when we're sitting down and says she's pretty cute and blonde but not his type.

This is the sort of thing that always happens to me.