A confession from her past in front of my friends that changed things forever. [Cuckold]

During our summer vacation in college my girlfriend Anna and I spent a weekend at the beach with some of my friends. We were about 12 people in total and at the time we had been together for about 3 months. Anna was super hot and way above my league so it was normal for people to be surprised she got together with me. I could see my friends checking her out all the time especially while we were on the beach.
One night tho we were having drinks after midnight and as we got a hit drunk we started telling stories and daring other to confess about things they had done.

While it started simple things went sexual pretty quickly and one of the girls there asked Anna if I was the biggest she had ever tried. She got an awkward smile on her face and tried not to respond but after everyone insisted she replied I wasn’t. It was a bit embarrassing but what came next took it to another level. A couple of rounds later a friend of mine John, trying to mock me asked her how big was the biggest cock she had tried.
I thought she wasn’t going to say anything but without hesitation she replied that it was about 9 inches.

Everyone’s jaws dropped. There was a silence for a couple of seconds until another girl there asked her for more info. For the next 2 minutes my girlfriend went on telling us about how a couple of years prior she dated a black guy who was an athlete. He was pretty huge about 6’5 very muscular and as she said before, had a huge cock. I felt my stomach upside down. I could see how the girls were so curious to ask more while the guys seemed embarrassed. She told us enough info but another girl asked if he was the only black guy she had dated.

Anna looked at me for a split second and replied that he wasn’t and that she wouldn’t provide much information about it. My friend Tom broke the awkward situation asking her what the hell she was doing with me and everyone started laughing. I felt so humiliated but tried to play it cool and laugh. For the next two hours of us being there I could stop thinking about my girlfriend taking huge black cocks. I never asked her much about her past but I never thought she had tried that much.
I felt my cock getting hard but tried my best to hide it.

Once we went back to our room I had a thousand questions I wanted to ask her but we were quite tired and went immediately to sleep. All night I thought about it and the next day as we were hanging out at the beach I decided to bring up the topic. What I learned really changed the dynamics of our relationship.