Headache for weeks with blurred vision is there a chance it might be brain tumor ?

When you ask the question "Is it possible"?, the answer is almost always "Yes" it's possible! However, statistically, brain tumor would not be the most likely reason. Certain other conditions, including, Migraines, traumatic brain injury, eye strain, hydrocephalus, also an entity called "pseudotumor cerebri", can all lead to similar issues. A CT or MRI would likely help to get to the root cause.