Symptoms after abdominoplasty surgery with lipo: Twice I had dizziness, nauseous, excessive sweating, and fainted.

I am 3 week’s post abdominoplasty with lipo surgery. Twice I had dizziness, nauseous, excessive sweating, and fainted while changing my dressings and gauze on my legs where I have the drains. The right drain was removed day 15 from the day of my surgery. Why am I having these symptoms? At first, I thought it was lack of eating. But now I am eating 3 meals a day and drinking 128 oz of water.