Hi, 19683. I think you misread "low blood pH" (acid/alkalinity) as "low blood pressure?" Here's a few admittedly random ideas -- links can be copied and pasted into your web browser address bar.
Chronic low blood pressure (hypotension) is not uncommon and can be caused by such factors as high blood pressure medications, pregnancy, diabetes, arteriosclerosis, and dehydration. Postural hypotension is faintness when standing up quickly -- deal with this by standing up slowly and avoiding fasting (maintain blood Sugar levels).
Salt, sugar, and caffeine can raise blood pressure, so moderate, intelligent intake of those can provide short-term assistance.
Diabetic ketoacidosis is a complication of diabetes mellitus caused by the buildup of by-products of fat metabolism (ketones), which occurs when glucose is not available as a fuel source for the body. A fruity breath odor and low blood pressure are two symptoms. http://www.nlm.nih.gov/medlineplus/ency/article/000320.htm