@Nazareno catching covid does not "build" your immune system. Infection-based immunity is extraordinarily fleeting and does not pay dividends on the damage the virus has already done, even in asymptomatic infections (which you may have had). Symptoms are not the same as underlying disease. HIV is famous for starting as a cold and then doing all of its damage silently

Furthermore, the immune system is not analogous to a muscle that needs to be used to be kept in shape, and the complete opposite is true -- there is no material benefit to any amount of viral infections. The immune system stays stronger the less it is activated, because it is ultimately a finite resource

With SARS-CoV-2 in particular, there is evidence that it sticks around and causes chronic T cell activation. There are only so many naive/undifferentiated T cells the thymus can supply before it shrinks (it normally shrinks with age)