I've been elevating my legs overnight due to fluid retention when I wake in the morning the swelling has gone but now they've swelled up again!

Fluid retention. When you lie down and elevate your legs, the edema fluid leaves your legs and goes into your blood and you have increased urination at night. That's why your legs are less swollen in the am. During the day, water goes to the most dependent part of your body, your legs. At 29, you are not expected to have edema. See a cardiologist or a neprhologist to find out why you do. Good luck.