hello and welcome to HCM,
I can understand your problem regarding the severe headache
Since you already have a tendency for migraine, the sinus headache
will be more severe especially in case of acute sinusitis
Since you have already started antibiotics i would recommend you to continue the same and also advise you to take injectable antibiotic and painkillers for better and faster symptom relief.
You also need to do steam inhalation and also take only warm fluids
You are saying that you very rarely get sinus infection
but since this episode is so severe it is recommended that you get a proper evaluation done by endoscopy
and also a CT of the sinuses and get back to me with the reports.
get well soon and take care
Dr Sriram Nathan