It's the unbroken silence that's killing you.
If it weren't for the fact that you'd practically been robbed of your old wardrobe and forced to sit expectantly in this lavish yet dim room donning nothing but the black, form-fitted dress you'd been given to wear, you would've been less anxious right now. But while you sit across from Negan, staring idly down at your lap while he loosely manspreads on the couch adjacent from you, you can't help the pounding beat your heart creates against the confines of your ribcage.
The only reason you were here was because of your own slip-up. Trying to steal from the Sanctuary's rations and escape was apparently a common occurrence and not so easily done. You were caught red-handed and fully ready to die by Lucille's (Negan's dangerously decorated baseball bat) hand but instead this was the opportunity you were given to redeem yourself. And it wasn't nearly as bad as having your head crushed like a watermelon, so of course you took it with little to no reluctance.
He's not visibly eager by your current attitude, quite the opposite really. But it's evident in his gaze how much pleasure Negan is taking in your adamant silence. It's as if he's testing you. Your resilience, both mentally and emotionally. He knew why you'd taken his offer to be in this position at his side along with the other wives he harbored in this freak ass harem. Negan has you at a disadvantage with that.
He wants to see how you'd hold up against the pressure and for how long.