Most blood pressure in older individuals are essential hypertension
which means that there is no specific cause for it. But in a few people it can be due to secondary causes which can be due to abnormalities in kidney
, renal arteries, endocrine, cardiac etc. This is called secondary hypertension
When an adult is diagnosed to have hypertension say after the age of 35 most doctors do not investigate for secondary causes as it is assumed to be essential hypertension. Most people need two or three medications for control of BP. Some people need even four tablets. When you start a new tablet it takes at least 10 to 14 days to have its full effect.
I hope you are under treatment from a good doctor. If you are taking medications as per the advice and if you have reached four tablets stage and at least 10 days have passed since starting the last medication then it is time for you to have a detailed check up for secondary causes of hypertension. Take an appointment with your doctor and ask him about the chance of having secondary hypertension. If you think the doctor is not competent then find another good doctor or find a specialized clinic for hypertension if available.
Home checking BP machines are mostly unreliable. So always check BP only with Mercury sphygmomanometer which most doctors use in the hospital.