Keep a log of when you take a pill (or 1/2 or 1/4 of a pill) and also record your BP in a log, either daily or twice daily.
Your doctor will be much more likely to go along with your self treatment if you can demonstrate objectively the effects of the treatment.
My dad did something similar. One of his pills made him sleepy, and a second pill have him nausea. He experimented with combining the doses and came up with 1/4 of 1 pill and 1/2 of the other, to get better results and no side effects from either. But since they are produced by two different pharmaceutical companies I can't ever see there being a clinical trial demonstrating the efficacy of taking them in combination the way he did. His doctor was opposed to it, but once he saw the logbook, he was ok (and i guess, seeing the writing on the wall).