The 5-foot gymnast made the revelation in an interview with USA Today this week ... just a few months after she left Auburn to get a handle on the ailment.

"I couldn't fit into any of my clothes," Lee told the outlet. "My eyes were swollen shut. It was just so scary."

Thankfully, Lee says she's doing better now ... and, according to USA Today, she looks "very much like the gymnast" who competed in the Games nearly three years ago.

"I haven't had a really bad day in a while," Lee said. "But in the beginning it was like I was waking up swollen. My fingers were so swollen they wouldn’t fit into my grips and I couldn't hold on to the bar."

She added, "My whole body was swollen because I was retaining water, so I couldn’t do a flip. … So it was really different and I had to learn how to work through it."

Lee said she's made some changes to her diet -- eliminating a lot of her sodium intake -- which has allowed her to reignite her pursuit of more medals at the 2024 Olympics in Paris.

"We're still working on trying to figure out how to balance all of it because I do have good days and bad days," Lee said. "But with the good days I just take advantage of what I'm able to do, and on the bad days I just do basics and try and stay as safe as possible."