Milf MILF borrows my girlfriend's boyfriend's penis

I had to run some errands, so I left my girlfriend at home. When I got back, I found her in the living room with another man. It turned out that my girlfriend had been cheating on me with my best friend! The sight of her getting fucked by another man was too much for me to handle. I couldn't believe that she had betrayed me like that. But as I watched her getting pounded, I couldn't help but feel aroused. Watching my girlfriend get fucked by another man was actually turning me on. I could see her tits bouncing up and down as the guy fucked her hard. I could see her pussy getting stretched out by his big cock. It was a sight to behold. And as I watched, I started to stroke my own cock. I wanted to join in on the fun and fuck my girlfriend too.