I have high blood pressure 179/117. I have had an ecg, echocardiogram, chest ex ray, stress test & they are all very good. What could be causing this?

Look deeper. There are multiple possibilities. The first come to mind is kidney problems, the second is hardening of your arteries, the third could be neurological. Your medications, sodium intake can also contribute to this. You need to look deeper to find the cause asap. It is dangerous to dismiss this high of a blood pressure! wishing you well...
Way too high. If that is truly you BP , you need to be on medicine ; normal tests does not mean you can't have essential HTN , and this needes to be treatmed and looked at to r/o other causes.