Why is he making me feel like crap for not letting him sleep with a guy?

my boyfreind of 2 years just admitted he is attracted to guys.he thinks he is bi-ual. now that i know he is always asking me if id let him try it since he has never done it before. im not into that all all. hes making me feel like im in the way of him doing what he wants, but at the same time he still wants me as a girlfreind. hes pretty much always asking me if he is allowed to cheat and when i say no he pouts. he really making me feel bad. we both love eachother dearly but how do i make him stop asking me if i can let him have with another guy. he doesnt even know if he is gonna like it or not. but when he does anything with a guy im gone. does he really want gay more than me. but he is always ensuring me that he loves me and never wants to leave me. he wants me to let him because he is confused. if he does it and he hates it then ill be gone but if he does it and likes it ill be gone anyways. how the heck can this work. why cant he just find the urge just for me only me and only love me