Weight gain after weight loss

I have been keto now for almost 4 weeks.  I lost 6 lbs the first week. Then the secon week till now I have had the keto flue. Last week the scales said I was down another  25 more lbs  I’m still sick but this am the scales said I gained. My 31 lbs back. Being so mad I took a hammer and busted those glass scales. Now I have to buy another one.  So what am I doing wrong  any advice will be read.