Hi.. Welcome to HEALTHCARE MAGIC. I have gone through your query and can understand your concerns.. As per your complain in case if you have sinus infection secondary to flu along with medical history of underactive thyroid, kidney transplant and diabetes and allergy to Penicillin.. You can consult an Otolaryngologist and get evaluated and he can advise you antibiotics other than penicillin like Azithromycin or Clindamycin, anti-inflammatory painkiller like Advil, decongestants like Phenylephrine, do warm saline gargles, steam inhalations, saline nasal irrigations and use a humidifier in your room.. Avoid spicy and chilled foods and sip on plenty of warm water.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora..