Most likely your blood pressure has little to do with your hangover. Essentially, it would up your circulatory system, so the alcohol would hit you faster, but also be worked out of your system faster.
Your hangover is most likely due to having drank shitty beer like miller (strike 1: beer, strike 2: shitty beer) You were asking for a hangover! Your empty stomach would contribute to your hangover by letting your body soak up the alcohol a lot faster, without any nutrients to replenish itself with after the slight poisoning a night of drinking will bring.
You should drink a gatorade, and eat something easy to digest; give your bod a break! ;p