Why did you get a Brain MRI done ? Is there is any other complain other than swollen tonsils ?
There could be multiple reasons behind neck pain. Detailed medical history needed. Your swollen tonsils might be an additional unrelated finding with another disease responsible for neck pain.
Have you been visiting a neurosurgeon/neurologist ?
Kindly consult for cervical spondylitis/disc prolapse - in which case you might need an MRI whole spine screening.
You would also like to have your lymph nodes examined by an expert.
Get your complete blood work up done. If needed,csf work up too. Check your
thyroid levels.
check with an ophthalmologist for any change in power.
Identify any stress area in your life, try to eliminate that.
Treat tonsillitis with saline gargles/steam inhalation/broad spectrum antibiotics sos.