When one considers the precision these valves must have not to leak considering they are just flaps of tissue that must align perfectly every time the heart beats it is not surprising that with time a little leakage occurs. Some leakage is normal. If you hadn't had the echo you wouldn't be worried. All your tests are fine and continuing your exercise should not affect the valves.
i understand your frustration, but the good thing is the leaking is slight. lot of people have some leaking and do fine. however, no matter how well we try to mainatain our bodies, chances are one way or the other we will have trouble. doctors usually say getting sick has an environmental component(which we can control by exercising, eating well....) and a genetic or biological component which there is nothing we can do about. the good thing is you've been very active so far, which might have helped slowing down the genetic component. our heart valves contain fibers that reinforce them and strings that keep them from prolapsing. sometimes, these fibers and strings are not as strong as we would want them to be, and there isnt much we can do to prevent them from breaking down untill things get bad enough for clinical intervention. depressing news but so far there is no other way. at your age, i would reduce the amount of physical exertion you're putting on yourself and keep it to just the amount needed for physical fitness while emphasizing on proper nutrition.