Hi I Have Been On Fluoxetine Because Of Panic Attacks

Hi I have been on fluoxetine because of panic attacks . I normally take two tablets at six but recently I Stopped taking it without consulting a doctor i felt fine at first but have started getting panic attacks again. I then decided to start taking them again so I took two tablets last night but it was at 12 at night. I the took two tablets again Today at six so that's four tablets in the space of about 18 hours is that a safe dose to take?