Going behind your back? No thank you. [His brows drop down in a straight line.]

And I hope that you understand I don't want things taking place behind my back, either. If it's something it would bother you for me to see or know about, then assume it's probably something that shouldn't be happening. Flirty or otherwise.

I am sorry if that's what it felt like to you. I believed that you would know anything in front of you wasn't even slightly serious. That I'd not disrespect you that way.