I have been suffering from dizziness for about a month now.Although it is not affecting my daily life(I can still drive my car without any problem),but I'm getting really uncomfortable with this.My dizziness worsens when I'm standing up.

I went to see a doctor and he advised me do a full blood test.
But the blood test result show everything is normal.And he prescribe me a few medicines and I have been taking them for 1 month already,but my problem still exists.

I'm just worried that the dizziness problem might be caused by a brain tumor.Do people suffering from brain tumor have the same symptoms as mine?Or is it much severe?