Didn't know you had DSPD, exactly.
Keep on trying, nevertheless. I've known quite a few cases of false or imprecise diagnosis, which led to situations like this, until one doc tried something different that finally did the trick. I could recommend you a few, but I doubt that this will be very helpful for you.
But if you really do have to live with it, why not make something out of it? As long as you are about as productive at night as other people are during the day, I dare say you still have some very good job prospects for example, in case you can get the right contacts.
It's up to us to use our disorders to our — and other peoples' — advantage.
If that sounds anywhere as motivating as I hoped it would, and in case you can take something out of this for your own life, let me tell you: It's nothing to be depressed about, it's a part of who you are. Not better or worse than other people, just different. =]