I'm a 24-year-old and I've been using Viagra to have better sex. I'm worried because it's become a habit, and over the past year, my penis isn't getting as erect as it used to. It would get hard about 2 to 3 times a day before, but now it doesn't. Even during sex, it gets hard but goes soft really quickly. I'm wondering if this is happening because of the Viagra, and Id really like some advice on what I should do.