Are you on lisinopril? Dry cough is a common side effect, but usually not the cold-flu symptoms. You can ask your doctor about possibly changing to a different class like an ARB class and see how things go. Difficulty concentrating could be from your BP not getting in a good range. Continue to monitor your BP daily on the medication to make sure it's not still high or even going too low on it. I'm sure your doctor discussed with you natural ways to lower BP such as weight loss, daily exercise, and cutting back on caffeine and salt, so continue to focus on these things.