Dont know what to say.

I have always had a hard time expressing my feelings to my husband or to anyone. But recently I seen some messages on my husband's phone between him and another guy he told the guy that he really wants to experiment with a guy, I asked him about it and he said he never did anything and that he would have chicken out if he even had the chance. I live him and believe him because he has never in 5 years gave me a reason not to trust him. My problem is I want to talk to him about it but I have no clue what to ask and even thinking about it makes me upset. I need help talking to him about this, any suggestions?