Sounds like fluid when you fluctuate that quickly, have you had your heart checked?

I have to weigh every day because of fluid retention. If I go up by more than 3 pounds in a day or 7 pounds in a week then I am suppose to call the doctor's office. I can go weeks with normal fluctuations and then all of sudden pop goes the scale.
I have Metolazone on hand in case they want me to take it. It does drain the fluid! I do find that mild regular exercise and strict salt intake helps me the most.

Typically, this is caused by fluid retention. You should notify your doctor of this significant weight change. Some PAH medications can cause excessive fluid retention/weight gain. Are you on a diuretic? If not, you probably should be. If you are, you may require a higher dose or medication change. With PAH, the recommendation is strict adherence to a low sodium diet. If you are not on fluid restrictions, it's always helpful to drink more water to flush excess sodium out of your system.

Edema (fluid retention) is more than likely the cause. This will fluctuate often.

Your heart is working against your pulminary artery and not clearing out your fluid. You need to be on Lasik and Potassium.