What do you consider being straight or gay? Finally, let's clarify once and for all: Would he go out and kiss an entire boyband? If he says he is straight while he's in bed with you, then he is straight. If he's dated girls before, you might assume he's straight without even thinking of the possibility that he could be open to getting it on with guys as well. Non-consent will result in ComScore only processing obfuscated personal data. Do you only feel confident in your attractiveness whenever you can "turn a straight man gay"?
You need to communicate that:
My boyfriend kissed another man: does that mean he's gay?