I'm with mammo, try and get into a Gastroenterologist. They should be able to find out whats going on. And if they can their probably more knowlegable about other avanues you should persue to get to the root of the problem. Good luck and hang in there.
Your PCP is useless with this, you need to see a Gastroenterologist for an evaluation. This is their specialty, and they will get to the problem quickly. You are very young to have high BP, have they done blood work to determine the cause of your high BP? At this young an age, there is an underlying cause. It can be caused by kidney or hormonal problems. I would see an Endocrinologist and get a thorough work-up. If everything is okay there, then see a Cardiologist to determine what is causing this high BP. Take care.