Boyfriend going to prom with another girl

Okay so I’m a sophomore and have been dating my boyfriend for a year and a half. There’s a rule at my school that underclassmen can’t go to prom and my boyfriend is a senior. He says he doesn’t want to go to prom unless he has a date which I think is just weird but I think it might be because the rest of his friends will have dates. I really don’t want him to go with another girl. It would hurt me so bad but I don’t want him to not go his senior year. He isn’t flirty or anything and I trust him but it would still suck seeing him to get pictures and all dressed up with someone else. Would you guys be okay with your boyfriend going with another girl to prom if you trust him and stuff? Idk if it’s just me:(