I'd talk to your area's superintendent, and see if he can't do anything, or see if he can't at least expedite the process. I really think something crooked must have happened. You should be able to get copies of the law that states that your diploma is not a standard high school diploma, and lists the differences. I know from experience that if you request them, the administration there is required to get them to you at in a reasonable amount of time, and at most, charge you for the price of paper they used. If they won't do that for you, they are illegally trying to hide something, and you really may want to consider hiring a lawyer.
I found out my senior year at high school, that most of the people, even with those who are elected, are very crooked, and have twisted ways of running things for their own benefit. This probably isn't the case in your scenario, but be wary, they used false techniques, trying to use the age of minority against students where it didn't, by law, apply, and hiding codes, rules, and laws from students, then changing them and not letting people know until the effects had been laid out. On top of that, school campuses had a zero tobacco policy, and they guy in charge of it all sat in his office all day long, chewing on a cigar, which, in this case, would be against the rules for my school system, and would result in some problems, if it were investigated. Anyways, long story short, beware, because they could be crooked.