Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain the symptoms of itching over the roof of mouth and bad taste along with nausea seems to be probably due to sinus drainage also known as
Post Nasal Drip and as the drainage is infected mucous can cause infection in the throat,palate and also cause bad taste and nausea..
I would suggest you to consult an Otolarynogologist and get evaluated and he can do a thorough clinical evaluation and investigations like throat swab culture can help in diagnosis..
You can be given a course of antibiotics like
Augmentin, anti-inflammatory painkillers like
Ibuprofen and along with it mucolytics like
Ambroxol and warm saline gargles can help..
Avoid spicy and chilled foods..
Chew
Vitamin C pellets..
Hope this information helps..
Thanks and regards..
Dr.Honey Nandwani Arora..