Boyfriend not coming to graduation. Help?

Hi my boyfriend and I have been dating for a while and things have been going very well with us. I am graduating from high school and he is not going to be there. I just dont understand. he has been wanting to go ever since i became a senior and now that june finally rolled around he is spending the day tomorrow with his dad. i'm kinda frustrated but he is the type of guy who puts his family between anything else. he wont cancel or reschedule if family needs him but when i need him, he's not even going to be there. Oh and by the way I would appreciate possitive answers and nothing like "just leave him"... i cant. I am pregnant. Thank you in advance for your kind, sympathetic answers. Maybe when we become a family he would put me as a priority? Personal situations are welcomed.