You dont need to take testosterone unless you are planning to get into bodybuilding.
The most important thing to bring your test levels back to normal is diet. And by diet I mean micronutrients. All the essential nutrients that your body need FIRST. Second, macronutrients. For hormone levels specially important to consume plenty of cholesterol and animal fat. Without it, the body CANNOT synthesize testosterone or any sex hormone.
Once you have your nutrition covered, THEN and ONLY THEN, exercise. Exercising without proper nutrition is just accelerating the aging process.
NEVER, NEVER listen to an MD doctor about nutrition. They have no knowledge nor scientific studies about nutritional science. An MD receives at most one semester of nutrition while in Medical School, simply because nutritional science is not their field. Their field is trauma, allopathic reductionism. I.E., drugs and surgery. Thats it.