I need advice about what to do with my boyfriend?

He committed to a family get together this holiday because he lives 45 minutes away from my family. We are having a huge get together and a big dinner one night. I asked him a month ahead of time because he tends to flake out sometimes. He told me yes if he didn't have anything with his family. His friends told him there was a big party right in front of me a week later and he got so stoked and totally forgot about my family dinner. He knows it is super important to me, my grandma is sick and my other family members have been wanting to meet him for a year now. I told him that there was my dinner that night and he said sorry I am going to the party. I understand that he wants to see his friends from back home, but this dinner was so important to me and he doesn't even care. I told him it is important to me and he said I am going home to spend time with friends and family. That really insults me that I don't fit under either of those categories for him. I asked him to take 6 hours out of his 2 weeks vacation time and he can't even do that for me, he would rather go to a party. I wouldn't be as upset if he had just told me he couldn't come. Am I overreacting? What do I do? I feel like he doesn't care about my feelings anymore.