Is high blood pressure hereditary?

I am 19. Every time I go to the doctor, I get very nervous because of past doctor visits. My blood pressure is always around 140/90. The doctor was suggesting I take high blood pressure medication but I believe I can get it lower without medication. My dad(started taking medicine when he was 20), mom, grandma and grandpa have high blood pressure. Do I just need to change my diet? Exercise? Or because I am nervous that causes it to increase?