Stop Please!!!, You Are My Boyfriend's Best Friend And This Is Not Right.

My boyfriend's best friend is giving me a massage and suddenly he puts one of his fingers in my tight pussy, a moan escapes me but I tell him to stop, he continues and I continue moaning, I feel guilty about it. What I'm doing to my boyfriend but I was so excited that I let him continue until I had many orgasms, I love his fingers in my wet pussy.