Caught My Boyfriend with Another Woman and Felt Envious

I caught my boyfriend fucking another woman last week. She was on her knees, sucking him off like a pro while he stood there, balls deep in her mouth. I watched them from behind the door, hard as stone, feeling my own cock twitching. Watching him cum in that slut's mouth turned me on more than it pissed me off. I left them alone and found myself jerking off to the memory of his face, lost in pleasure. It made me question our relationship but also strangely turn me on, knowing he could give another woman what she wanted like that.