Does a negative non contrast mri rule out chance of having a brain tumor? or is contrast needed?

Most of the time: Usually it does. Most of the time it will show the tumor outright; some very benign or slow growing tumors may be very difficult to see without contrast, but there will usually be clues or some alteration of the anatomy to show that something is not right.

Highly likely: No imaging is perfect and sometimes readings are inaccurate but more often reliable. If you wish reassurance contact radiologist and discuss