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You are now >14 days from symptom onset of your Covid infection and you report not having moderate or severe immunocompromising condition. So, despite your prolonged symptoms of cough and sinus congestion and drainage, I think it is okay for you to leave isolation. The symptoms you are experiencing may be just the prolonged healing process that many encounter and does not involve active live virus in your system.
However, if it is possible that you were exposed again to another infection (a second infection since January 25, because of a symptomatic household contact or other reason), then you may need to reset the isolation clock to that last time you tested positive.