Per current CDC’s guidelines, there is no need to quarantine if your test was positive in the previous 3 months, and you have recovered and remain free of COVID-19 symptoms. The sensitivity of COVID-19 PCR tests in discovering viral RNA is very high and it is not uncommon for individuals to have positive tests in the wake of an infection for up to 3 months. The 3-month span extends from the end of your isolation period from your infection with COVID-19. Thus, the 90-day period would begin 10 days from symptom onset, or 10 days from the day of a positive test if you have not had symptoms. At the end of the 90-day period from your last infection, you would resume all the usual CDC guidelines for quarantine and isolation.