My boyfriend doesn't want to go to my senior prom?

June 4th is my senior prom and he doesn't want to go with me. He is 20 and his excuse is "I didn't go to mine, why would i go to yours?" which is messed up, I know. Also he exclaims he is too old. He tells me to go with someone else. He is being really stubborn and he insisting he don't go. How do I make him change his mind. Prom is important to me and I want the memory to be with him not by myself because no one else wants to go with me :( (Don't just tell me to dump him please) thank you in advance<3