Bf & date parties

My bf is a year older than me and is a freshman at ua. He’s in a frat but I don’t really know much about date parties and things he gets fined for not going to. He’s been to many date parties yet whenever i ask how they went, he changes the subject. I trust him but not really the girls around him bc if he asks a girl to a date party who knows what the girls think his intentions are. once i started like asking more about why he never tells me what happens at these parties, he stopped going to date parties. He didn’t tell me he doesn’t get fined for date parties until he had already been to multiple so I don’t understand if he doesn’t get fined for date parties, why does he still go? I understand maintaining relationships with brothers but I saw some responses saying he can just take a roommate or just a guy friend or even go alone instead of finding a girl. He also has taken the same girl multiple times and i don’t really know if there’s something going on. He gets upset whenever i ask but i feel like im being valid whenever i question this. What do you think i should do?