At your age, having a level of testosterone at 2.89ng/mL is right where it should be. There are several symptoms associated with lowT which include high fatigue levels, decreased libido, and even mood swings. It might be stress or some medical problems causing it; see a doctor before taking testosterone because if not done properly this could harm your body. If you sustain your exercise routine, eat well-balanced meals daily, and have adequate sleep every night -these activities will help maintain normal levels of this hormone.