A naturopathic physician has completed a 4 year doctorate program in natural medicine. This means that in a state where they are licensed, they have nearly Identical prescriptive rights as other medical professionals. A naturopath who has no formal education or state licence would not have this right or responsibility.
Second, make sure you speak with your medical provider if your medications are causing some unwelcome side effects, that way they can possibly change medications and or dose.
That being said, there are other prescriptions medications on the market that may be a better fit for you and your high blood pressure than only Lisinopril. The other, not pharmecutical methods for controlling blood pressure are many. Stress reductions, diet, exercise, and some herbal preparations can all be effective and have a place in a blood pressure lowering health plan.
Speak with your doctor about these other options. As you fit in exercise you may find you need less and less of the medication that is causing your problems.