The official recommended guideline is to isolate 10 days from when you started symptoms and complete the 14 day quarantine from last exposure, whichever ends later. This section is very technical but will explain this official guideline in further detail.
Because you have COVID-19 symptoms, a 10 day isolation from the date your symptoms first started should be completed in case you have COVID-19. However, in case these symptoms are not a result of COVID-19, because you have been exposed you must still complete a 14 day quarantine from your last exposure date to watch for new symptoms that could be caused by COVID-19. If your symptoms started in the first 4 days of your 14 day quarantine period, your isolation/quarantine time is completed at the end of the original 14 days. If your symptoms started between days 5 through 14 of your 14 day quarantine period, your isolation/quarantine time is completed at the end of your 10 day isolation, which will take you beyond the original 14 day quarantine time. A positive COVID-19 test can simplify these timelines to just a 10 day isolation from the date your symptoms first starting. Any isolation/quarantine time should not end until your symptoms have improved and you are free of fever for more than 24 hours without the use of fever-reducing medication.
Isolation – “As much as possible, stay in a specific room and away from other people and pets in your home. If possible, you should use a separate bathroom. If you need to be around other people or animals in or outside of the home, wear a mask. Tell your close contacts that they may have been exposed to COVID-19. An infected person can spread COVID-19 starting 48 hours (or 2 days) before the person has any symptoms or tests positive. By letting your close contacts know they may have been exposed to COVID-19, you are helping to protect everyone.” -CDC
Quarantine – “Stay home for 14 days after your last contact with a person who has COVID-19. Watch for fever (100.4◦F), cough, shortness of breath, or other symptoms of COVID-19. If possible, stay away from people you live with, especially people who are at higher risk for getting very sick from COVID-19.” -CDC