I've got a feeling it's the change in diet. I'm having a similar reaction and I see on another thread some believe it is a lack of fat causing the "congestion." Well, I'm actually eating less volume of food and that's obviously part of my cause. I am also noticing that I am eating too high a percentage of carbohydrates for the purists here. I am losing weight because I am just eating less calories, and, I am still getting my lifestyle in order so will no doubt be eating more animal fat in due course.
Why use a sledge hammer to crack a nut when a steam roller is even more effective, and, is fun to drive.