Swimming laps symptoms and conditions

So I just read through a few of these and have to admit a similar story. I am 26 years old and have hereditary high blood pressure due to polycystic kidneys. My doctor put me on 20mg at first. I have always been an avid exerciser and after about 3 months on the drug I was in the pool swimming laps and my arms completely cramped up and started spamming, had no control whatsoever. My best friend's dad is a neurologist and his mouth about hit the floor when I told him how many mg of lisinopril my doctor had prescribed. He immediately cut my dosage in half. My symptoms have still progressed and I am officially stopping taking it because I have had heart flutters and palpitations that would scare any normal human being into thinking they're dying. I also have the shortness of breath, dizziness, numbness and tingling in all of my limbs, odd pains I have never had before in the most random places such as my forearms, calves, abdomen, and I feel like I have arthritis! NONE of this EVER bothered me before I started taking this medication and it has taken me months to actually come to the realization that these are not signs of aging or fatigue. I'm a healthy 26 year old female who exercises on average 5 days a week with low-fat high fiber diet. Point of my story: this drug claims to be the best on the market, but something tells me the doctor's push is coming from pharmaceutical endorsements!!!! Beware of the poison.