I'm An 80 Year Old Male. No Recent Med Changes.

I'm an 80 year old male. No recent med changes. Take meds for HTN, cholesterol, diabetes. I take Corgar 6.25 mg BID and feel like the pm dose gives me pallpitations, dizziness and a feeling of "empty head" and extreme fatigue. I take it w Metformin and Lipitor. They've done many tests, including, Echo, MRI, arteriogram... they all seem to be ok. Any not so common side effects associated w Corgar that could be causing my symptoms?