Hi docs i was wondering i was using an old toothbrush when i had mouth ulcer next day i had sore throat it's been over a week what is the cause of it?

I wonder myself: Not enough room here to list all the causes of sore throat and mouth ulcers. May be related or coincidental. Please see your Dentist for a full medical/dental history, a comprehensive examination, necessary lab tests and x-ray's, differential diagnosis, and focused treatment plan.

Get a new toothbrush: A sore throat can be the first sign of a cold and has nothing to do with your old toothbrush. Fortunately, most sore throats are caused by a viral illness and go away without medical treatment. Regardless, you should change your toothbrush every 3 months.