You're 18 and shouldn't be fucking around with anything that could possibly mess up your already sensitive hormone levels. Anyway, you should be fine. I'm guessing all you did was throw away your money on a useless product, spend that money on chicken and oats. I wouldn't be taking anything that has 0 scientific data backing it, research stuff before you take it :). Stick to creatine, whey protein, and maybe some caffeine before your workouts for that extra "boost".
Copy and pasting this straight from Wikipedia: The extract is claimed to increase the body's natural testosterone levels and thereby improve male sexual performance and help build muscle. Its muscle-building potential was popularized by American IFBB bodybuilding champion Jeffrey Petermann in the early 1970s. T. terrestris has consistently failed to increase testosterone levels in controlled studies. It has also failed to demonstrate strength-enhancing properties. However, many supplement brands claim effects of products that combine various herbs with T. terrestris.
Tribulus has been shown to enhance sexual behaviour in an animal model. It appears to do so by stimulating androgen receptors in the brain.
Some body builders use T. terrestris as post cycle therapy or "PCT". After they have completed an anabolic-steroid cycle, they use it under the assumption that it will restore the body's natural testosterone levels.