Had an upper raspatory infection followed by a sinus infection and ear infection. my symptoms are all gone and feel great but have mucus in my throat randomly, but my throat does not hurt. the lining in throat is a little red. it has been 3 months?

If that symptom occurs more in the morning after waking up, it is likely post nasal drainage from the sinuses although you do not have any sinus symptom. If the symptom occurs randomly throughout the day, the viral pharyngitis may not be over entirely. Patient with post covid-19 syndrome may have certain symptom(s) which last for months. Covid test is not sensitive enough to detect all cases.