That's what happens with low carb and cheat days. Protein pushes water out of our cells and carbs take it in, so it looks like a big gain after eating carbs. But a lot of it is water. Maybe try switching up things a bit. You might try zig zagging your calories high and low days to see if that might help jump start your metabolism. Switch up foods. Make sure you are getting in good fats. They can help us lose. Switch up your exercise. Add some intensity or duration, etc.