What Causes Heart Palpitations And Sweating While On High BP Medication?

I have high blood pressure or at least the last 15 years, and taking prescription meds. For the past year or so, I have been experiencing what feels like rapid heart beats coupled with sweating sometimes, and strong urge to urinate. This may last up to several hours at a time and then stops. I usually feel exhausted following this episode. Recently, these episodes have increased in frequency and duration. My internist has no idea what to make of it. I have regular check ups, blood wok etc., the results of all labs come back normal.