Masturbating to relax

Despite the comfort of Anna's bed and the extremely late hour, I was having trouble falling asleep again. The night's events ran through my mind constantly, keeping me agitated and aroused. My cock was laying across my thigh, thick with blood but not fully erect yet. Looking across to Anna's still form, I raked my eyes over her bare back, admiring the small sliver of her breast I could see rising and falling with her breathing. My cock gave a twitch, and I slipped my hand down to grasp it, trying to stifle my sighs.

Slowly, hoping I wouldn't shake the bed too much, I started stroking, moving my clenched fist along my stiffening shaft. I didn't know if I had enough left in my balls to cum again, but my cock was responding, growing harder with every stroke. I thought about Anna's curvy body, spilling out of her dress. I thought of her legs spread lewdly open, thighs glistening with piss and arousal. I stared at her smooth back, and imagined painting it with streaks of cum.

My masturbation was growing more aggressive, caution be damned. My elbow hit the mattress with a dull thump on every stroke, and the covers were shaking in a telltale way. I should be more subtle, especially given that Anna had only just forgiven me for doing the same thing. This night had been such a long, protracted tease though, and I desperately needed release from the thoughts plaguing me. Without warning, Anna rolled over to face me, her prominent chest jiggling with the movement.

"Hey Shaun? What did I say about wanking off on me again?"

My heart stopped, and I sputtered dumbly. "Uhh..."

"Well?" she prompted, hand toying with the covers that were doing nothing to protect her modesty.