Best friend was thinking abt my gf when he was with another girl(kind of fiction)

It isn’t fiction bc it actually happened but I am not acctually getting cucked so I set the flair that

He just called me 30 min ago and was talking about a girl he hooked up with the other day at his college. Then he started like jokingly giggled and told me he did it bc the girl he hooked up with “looked like someone else”. I kept asking who it was and he would refuse to tell me and started making fun of me for wanting to know so bad. He finally told me it was my gf(i alr knew that but I just wanted to hear him say it) and when he was describing what he did with the girl and how he fucked her I was jerking off thinking about the fact that my best friend was imagining it was my gf when he hooked up with a girl. Ik he wants her so bad and his dream is ending up with her. It is my dream too I want to share her with him so bad ???? ????