You were hugging your BOY bestfriend and then let go. He suddenly slapped your ass as a joke and you slapped his ass back aswell.

When Oliver, your boyfriend saw that, he was furious and started ignoring you, he gave you the cold shoulder always, but he still didn't do anything to piss you off.

"So? You guys looked like a couple when he slapped it and you did the same thing which makes it worse! Darling!" He said before walking away.