Severe headaches with recent onset or headaches that had gotten worse over time always warrants serious medical attention.
As your physician said, you must be examined with Brain MRI to rule out brain tumor.
This disease triggers a chronic, daily headaches, different from those you ever had before, are accompanied by nausea / vomiting, are made worse by bending over or straining when going to the bathroom.
Since you have chronic headaches for long time, you may have another condition leading to that, known as fibromyalgia.
It is well known that fibromyalgia sufferers have chronic headaches, difficulty concentrating and muscle and joint pain, and chronic dizziness.
You may feel extremely tired with whole body spread pain.
Dizziness due to fibromyalgia can last for mere seconds or as long as a few days, causing headaches, nausea, and even fainting spells.
"Fibromyalgia headaches" are chronic ones, in form of tension headache, migraine and combination of both types.
The first one is often felt at the base of the neck but soon work its way upwards, eventually spreading to the temples (feeling like a band tightening around the entire head).

See a neurologist!