Idk how to feel .. :( I need an advice.

Soooo..... My fiancé has his friend over and I'm making dinner for the 3 of us and they r talking about stupid boy stuffs and all the sudden his friend brings up how one time my fiancé was out drinking with him and other friends and he was looking on craiglist for a hooker ... I don't think it was something that needed to be bring up in front of me and it really irritate me . I know is not my fiancés fault  and is not like he did it while dating me but now I'm down n i know and being cold with him even if is not your fault I just can't help it to feel idk gross out ... Upset I don't really know how I feel ... This happen like an hour ago and since his friend left my fiancé tried to have sex  and I just couldn't stop thinking about what his friend said .