Several observations: The diarrhea from the amoxicillin can be a colon infection called C.Diff. enteritis...i would stop the amoxicillin and call your doctor. secondly, amoxicillin doesn't worsen a fungal sinusitis but it also doesn't treat it. You may need to see and ENT doctor.
Hi, welcome to the forum, your symptoms are suggestive of infective sinusitis. The causes of these are bacterial infection like streptococcal, staphylococcal, Tuberculosis, Bronchiectasis and Fungal infections.
You need to send the mucus or throat swab for culture, microscopy, staining to rule out the pathogen and should also take chest radiograph. Antibiotic sensitivity of culture will decide the effective drug. The green color mucus suggests pseudomonal infection.
If fungal infection detected it needs appropriate systemic anti fungal. As for pseudomonas anti pseudomonial penicillin or 4th generation cephalosporin against prescription are quite effective.
Antibiotics like amoxicillin and esp. ampicillin is associated with diarrhea. Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea and pseudomembranous colitis. I suggest you to consult ENT specialist for evaluation sinus block. Take care and regards.